In 1926, T. E. Lawrence ("of Arabia") decided to take his memoir about the Arab Revolt during World War I—Seven Pillars of Wisdom—and turn it into a slightly abridged but lavishly illustrated "subscribers' edition," with illustrations commissioned from some of the leading British artists of the day, including Paul Nash and Augustus John. Fearful of being seen to exploit his war-time record for personal gain, Lawrence published 200 copies at thirty guineas each, which was about a third of the cost per book. A trust was eventually set up to pay off the debt. Lawrence was no businessman!
We know this story because, way back, our own Martin Rowe was a research assistant to T. E. Lawrence's biographer, and it's struck us as a very interesting model for book publishers. Of course, one should price a project so that the amount you charge is equal to or more than the price you have pay in order to get the job done; but, in principle, it's an effective way for specialized books to get into print. Rather than print a bunch of books and hope that somebody pays for them, you ask individuals if they'd be willing to buy the book, get them to commit money up front, and publish the book for that number. Of course, the more "value added" you can supply the project, the more you can charge. In Lawrence's case, the subscribers edition contained original art, beautifully reproduced, exquisite binding, and other personal touches. Copies of these volumes now routinely sell for $100,000.
Clearly, this way of doing business is nothing new; but for publishers and would-be authors today, it's a very real option. Kickstarter.com offers a similar program. You set out the project you want to be funded and how much you want to raise, then you tell would-be funders what they're going to get if the money's raised. If you don't get all the pledge money, then nothing happens. Subscription-based publishing just might be the Next Big Thing.