OK, yes, it might save you the publisher's costs, but here are things you'd have to think about if you're going down the vanity publishing route: where will you get an ISBN and bar code for your book (most booksellers won't stock your book without them)?; how will you distribute the book?; who's going to do the marketing?; who's going to do the selling, ie how will you persuade the booksellers to stock your book. The latter point is difficult enough if you're going through a publisher, unless you're trying to push a known author.