…will cost you about US$250 according to this article [cnn.com] on CNN:
A mouse with arthritis runs close to $200; two pairs of epileptic mice can cost 10 times that. You want three blind mice? That’ll run you about $250. And for your own custom mouse, with the genetic modification of your choosing, expect to pay as much as $100,000.
This brings ups all kinds of bad Richard Gere jokes and Moral questions. All of which have been thoroughly discussed over at slashdot [slashdot.org].