I've read proposals that involve making it so that they're priced by pact type, but that doesn't really take into consideration the force or Edge of the spirit.

So what would you propose?

the force or edge of the spirit isn't really relevant to it's worth, imo.

low force spirits are more likely to be in danger, but also don't face dangers that are nearly as large.

high force spirits are less likely to be in danger, but when they are, it's gonna be something big.

imo, that balances itself out.

however, if you wish, i might suggest you require they buy the spirit as a contact as well, with higher force spirits having a higher effective connectivity rating.