In terms of escape, it's great - you can pretend to be someone else, some people really take on the role-playing, you build friendships and alone or together, you can conquer the world. Virtual or not, you may not think it's educational but you do learn a lot about stategies (ask pt - he's done many spreadsheets on damage over time and such), about patterns, people and team-work. All of that is skills that can be used in life and for introverts, it may be easier for us to achieve this virtually than in real life. I've learned a lot about people, stategies and how things work, I've even learned about politics, social drama and social taboos in these games. In my opinion, $15/month (although, I paid less than that), is cheap for that kind of information and education.
I've already said why I think it can be educational and I like the paid ones better than free ones because it filters out teens and younger, more immature people from the game - that way there can be proper information gathering and usually better game experience when dealing with multiple people online.
But have you tried the paid versions of online battles and character customization, it is a whole different level that free offline games can't even begin to simulate. It's a lot of fun in pvp and great for getting revenge and sharpening your game playing skills, you can't get the same satisfaction defeating a computer ai as defeating a real person (even if you may not know who it is).