The budgets to develop these games are usually reported in the multi-millions of dollars range
and even then less than half make it to market (after years of development), including major titles backed by solid companies, and despite huge established communities of eager fans.
Most recently cancelled: 'Ultima X' ... 'Warhammer Online' ... even 'Middle Earth Online' is looking like vaporware. The genre is clearly a massive gamble; tho IMO developers are now playing it too safe, resulting in mediocre clone after mediocre clone. The developers I'm rooting for are
http://www.darkfallonline.com/ , because they've really got the right ideas re: how to take mmorpgs in a better direction (away from the everquest model) but I'm not convinced they have the funding to finish this.