Yes, $250 isn't bad for an itemshop. That's 1-2 days worth of work for a skilled coder and its not a terribly long script. However, when dealing with genes that can be any colour, then producing a completely new image from many layers of two different pets that saves and displays itself... the layers, the time... It is a very complex code and its probably going to cost you a pretty penny (I speak from experience). If you're curious you can probably go to
Khimeros and ask Onyx how much it cost her to have Nas code her breeding script. If she's not too busy it can help you get a ballpark estimate on how much you should expect to save for a developer.