How much does fertility change a cost by?

I'm looking to buy a pup off of a user who doesnt have them listed for sale yet (though they have them in a sale den so it will likely happen at some point). The reason I wanted to buy them is that they have very low fertility, and Im planning on trying to gather a few for mutation breeding. The pup is honestly pretty average and doesnt have any other "selling points", but I want to make sure that I offer the right price and dont accidentally scam the other person. The user appears to be selling their other females at 100 SC so that seems to be the starting point.

TL;DR- What price should a very low fertility pup go for if they're average in every other way?