[Newticus]

I don't know about it being a normal price, but the rarer mutations of birds can cost more for a number of reasons. Depending on the genetics of the mutation, the parents may not raise only slate coloured mutation babies, which means it is harder to breed them. It also may have cost the breeder a large amount of money to aquire the mutations in the first place. I can't tell you if it's an unreasonable price to pay, but that is probably the rational behind the prices you have seen. There are lots of grey budgies out there, why not go for one that doesn't have a fancy mutation name attached to it.

Melanie