Salary/price negotiations are tough for anyone. But as you get a feel for your industry and see how others handle similar situations, you can build up some stock strategies for dealing with those initial inquiries (and handling the customer while you're providing the service).
For example, below is a link to an article on negotiating salary when you're first being interviewed for a new job. Interviewers will ask for a salary range early along in the interview process because they need to stay within budget or want to screen out applicants who are well outside an organization's targets.
That may not be the same situation as yours (which sounds more like contractor work if you're being asked for per-assignment rates). Still, it's nice to know how the rest of the world handles the situation of salary negotiations: Is it a tough question to answer? Should you provide a range up front or defer an answer? What are the standard polite ways to defer answering? etc. (If you want to read the article, you will need to register with the Washington Post. But the registration is free and won't generate spam.)
The article is entitled, "Surviving the Salary Negotiation Minefield." Basically, the gist of the article is that you should defer answering an inquiries about salary: "Your goal is to buy time to learn as much as you can before committing to a target salary. Even asking for 24 hours to give it some serious thought can give you enough time to run the numbers so you don't rule yourself out or sell yourself short..."
And of course the article provides a number of polite ways to defer and also suggestions on what you should be doing with that time that you buy yourself.
As for the situation of contractors setting prices on a per-assignment basis: I was an outside independent contractor (a translator) for about five years before being hired by my present employer. Now that I'm on the inside, a big part of my job involves contracting out assignments to outside independent contactors. So I've dealt with both sides of the situation.
Here are some ideas on how I handled price negotiations when I was an independent contractor.
1) As for initial price inquiries: I generally wouldn't provide a price without first seeing the work to be done. Translations vary greatly by difficulty, and the client often doesn't describe the work correctly over the phone since they can't read the material. If nothing else, that always bought me an hour or so while they faxed or e-mailed the work to me and I looked it over.
2) As for setting price: With the work in front of me (and having taken some time to deliberate when and how to fit in the work), I was in a better position to sell my services. For example, I could substantiate my price by describing the work that was required and simultaneously give a little sales pitch about my services. Even if I wasn't the cheapest translator in town, once I had the work in hand and had demonstrated that I was knowledgeable about the work and a good match for the job, it was often easier for the client to just leave the job with me than to try to shop it elsewhere.
3) If the client asked for a discount: One trick for handling this is to offer a couple different quality levels of service (say, a summary translation versus a full translation, or an expensive rate for a short deadline and a cheaper rate for a long deadline). If they refused to pay the full rate, I could always offer the cheaper summary translation rate. And when they asked what that entails, I could often talk them back up to the higher rate when they found out that the summary translation rate offered an incomplete translation. But in general, I've found that it's good to offer a couple different levels of service and price and a choice of trade-offs between quality and time (deadline) or quality and price. That seems to mollify customers even if they ultimately end up paying full price anyway, because at least they've been given some options rather than just having to swallow a single big price.
4) If a new client insisted on discount even for a fully polished translation, I generally went with along with that, especially if there was any hope for more work in the future from that same client. I could justify the discount (to both myself and the client) on a one-time basis in order to get my foot in the door and get my product in front of them, with the proviso that I would insist on full price for future jobs.
I've done the same thing with permanent jobs in the past. That is, when I breaking into a new field and couldn't justify a high salary based on past performance, then I would sometimes agree to work for an artificially low salary for the first couple months while I was learning the field with the proviso that after six months I would be back to renegotiate my salary and bump it up to normal levels. An arrangement like that allowed me to get my foot in the door at a discounted rate and still retain the right to demand a higher salary once I was up to speed and they were more familiar with my work.
As a result, I didn't think it was a big disaster to put up with some occasional discounted work, especially when I was trying to build clientele and/or get a foot in someone's door. If it's only on a one-time basis or for a short period of time, then it usually doesn't result in a big financial hit. Meantime I developed some goodwill with the client and showed them that I understood their fears about agreeing to a big bill before they've even seen whether my work fits their needs. I just covered my own needs by making sure I had the right to demand a higher fee later on once I was a known quantity.
Anyway, the big lesson here is to be prepared: Get in the habit of asking to see the work close-up before pricing it, be able to break down your services and give a sales pitch about them, maybe have some cheaper services to offer when clients can't afford the full rate, etc.
Also, figure out your priorities ahead of time. Giving out a discount once in a while won't hurt so bad if you can justify it as an investment in a longer-term working relationship. But again, that takes some preparation. You want to decide ahead of time when and under what conditions you'll give out the discount, so that you feel you're in control of it rather than feeling like you've been bullied or conned into providing a discount.
These are just a few general suggestions. Your mileage will vary, depending on your field and the nature of the product you provide.
When I was an independent contractor, ultimately I wanted to end up with one or two big clients providing a high volume of work. Those kinds of clients tended to have flat rates, and so negotiations weren't so much about basic salary; instead they were about things like working on weekends and holidays or trying to get a bonus for extra-difficult assignments. So I tended to cultivate those particular clients by providing a lot of personal service and high quality and taking the hit myself on occasional extra costs. I wanted to show that I was a compliant, high-quality, low-maintenance contractor. When I was first breaking into the translation field, I specialized in precisely those jobs or profiles that other contractors didn't like: for example, working on holidays or doing big overnight assignments without demanding extra money for the extra inconvenience. In the end, my big-volume clients said they kept coming back to me and moving me higher and higher on their lists of contractors (and thus giving me more and more work volume) because I was always there for them and I didn't nickel-and-dime them or give them a hassle about inconvenient assignments.
So sit down and figure out your priorities, depending on your clients and what kind of business you're trying to build. Again, do the preparation and figure out your priorities ahead of time, and then presumably you won't feel so bad when you occasionally have to swallow a discount or put up with some inconvenience in order to land a strategic job or client.
[Edit:] Oh yeah, and if you have to refuse a job, then it's a nice touch to give the client the names of some generic competitors. I've refused plenty of jobs in the past, especially once I was set up with one or two high-volume clients and didn't need outside work. Sometimes new customers called with a difficult, one-off assignment, and I was too busy already or I just couldn't be bothered taking on unfamiliar work. Nothing wrong with being in a position to turn down work. But just as a courtesy I gave them a read-out on what they needed in the way of services and steered them to an acquaintance in need of more work or even just an agency. That way there were no hard feelings, and sometimes acquaintances even got in touch later and thanked me for steering work their way.