Kittens are in short supply here too. People seem happy to pay big money for them. I give my kittens away to people I know, but have been known to put a £25 price tag on if anyone asks who I don't know. I am not in it to make money, but do not want my kittens going somewhere not nice, and think if they pay, they are more likely to look after them (well, thats what I hope!) but most of mine are with people I know, and I can see them when I visit too.
I cannot see that people are making much out of the kittens, if they have fed them, wormed and deflead them etc. although £60 is a lot of money. I have people willing to pay that for my white kittens (one of which is sitting on my knee as I type!)
My priority is a good home, and if thats where they are going, then they are free!