Hi OP! I've just finished a Creative Writing MA, albeit in children's literature and writing. I found it useful, but that's mainly because I work in a related field anyway, and this particular course had quite a large critical theory/social studies element that was relevant to me.
Creative writing courses are certainly not the be all and end all. I've heard many stories from friends and acquaintances who have taken the plunge, spent vast amounts of money, and now regret it - I hate to say it, but many (though by no means all) of them are essentially money-making vehicles, designed to tap the huge pool of wannabe novelists that's out there! Most of my friends who have done these courses remain unpublished, although a few have found agents via the networking aspect of the course.
As you've discovered, some of the fees (especially for the short courses that are run by commercial publishers/newspapers etc) are exorbitant. Having spent some time working in publishing myself, I know that many publishers are struggling and seeking alternative means of making money - thus the recent proliferation of courses.
For me, and most of my peers, by far the most useful aspect of the course was the opportunity to have our work heard and critiqued by others - but you don't need an MA to do this! There are many local and national writing groups you can join to share your writing with others. Personally I've joined the SCBWI, which specifically supports children's writers and arranges retreats, conferences etc where members can meet and exchange ideas. I've met some wonderful people through doing this, and I'm sure there are similar organisations for writers of adult fiction.
Finally, have you considered doing an Arvon course/retreat? I haven't been on one myself, but they come highly recommended by many of the people I've met via the MA and SCBWI, and they consistently seem to get the best speakers/writers attending.
Sorry that's all a bit waffly, but hope it helps - basically the most important thing is tokeep going and not lose heart, although I know from experience that it's easier said than done!