Least convenient world apples, but I'd bet Dumbledore and Flamel haven't been looking for cheaper ways to create more Stones, because it just isn't their goal. (And they're already in trouble because they have to guard the one stone from Voldemort.) If Harry knew, well, I'd bet his eyes would be ice and his voice would be distant darkness and... er, I mean, he'd go Librarian-poo crazy.