As someone who has written a number of chapters for edited books in my other life, IMO this isn't a very sensible business model. Normally, the publisher will set a budget for a book which will include the costs of editing, printing, distribution, payment to author(s) etc. and will rely on the sales to recoup the outlay and hopefully make a profit. If the projected sales don't cover the budget, the book doesn't get published.

Naturally the likelihood of sales will depend on the quality of the content, ignoring whatever promotional devices can be used to inflate sales, and therefore the publisher will want to attract the best authors (or in this case artists) with a track record of producing high quality copy to timetable.

The effect of the method used here is to offset the initial outlay and reduce the risk of loss by charging the contributors, but against that is the possibility - actually pretty near certainty having read the comments in this thread - that the best artists will not bother to contribute, because they don't need to. So you run the risk of the contributors to the book comprising the B team, as it were, with reduced quality and therefore reduced sales (and incidentally, reduced credibility if the exercise is repeated in the future). Doesn't make sense to me. (Speaking from the viewpoint of someone who no matter how many $$$ he forked out wouldn't get chosen!)

Steve