Unless you're actually tired of working in the field of graphic design, I wouldn't give up so quickly. I've known quite a few designers who earned good wages, and I work with a bunch of fulltime and freelance graphic designers now who all must be doing pretty well. I work for a consulting firm, and we have a team of graphic designers who are on staff full time plus a stable of part-time freelancers that we call on when things get too busy. Most other large consulting firms follow the same model.
If you enjoy working with finances, you might consider an art director job. That generally involves managing budgets and managing other graphic designers, coordinating traffic, etc., and providing overall direction and guidance on design projects. Many art directors make excellent money, and it's the next logical step up from graphic design. If you went back to school for accounting you'd be starting over from scratch; if you move up to art direction you're building on the foundation you've already created for yourself and your earning potential will be much higher due to your experience.
If after 15 years I couldn't manage to obtain "good wages" doing graphic design, it's doubtful I'd be able to any time in the future. I know having a negative attitude doesn't help, but I've been so positive for so long (15 years!), only to apply to job after job, and find out they're all offering the same $10-$15 an hour, and often in cities such as LA/Orange County and New York where the cost of living is so high, that those wages are the equivalent of close to minimum wage in other locations (and often alongside other graphic design jobs offering $8 an hour). I've been looking for full-time graphic design work for 4 years now (been freelancing during this time) with no luck. I also have several graphic designer friends who are no better off, and all have found other careers or are working retail.
I've tried applying for art director jobs as well, with no luck. They're even fewer and far between than designer jobs, and even harder to get in to. While it's possible, it could be years before I luck out and actually get one, and then I still have the problem of being in an unstable, over-saturated, cutthroat field. It's almost as if you have to *know* someone to get a good, secure, high-paying design or director job.
Also, part of the problem I'm having in finding work at this point is that I went to school so long ago, so I only learned graphic design for print. I never learned web design beyond very basic HTML.. I'm beginning to realize I'd have to go back to school *anyway* for Flash, CSS, and other web building topics at this point (and I do NOT like web design at all, from the few basic sites I've built), so it seemed like a good point to consider a switch to a much more stable career that isn't way over-saturated like design is.