Steam doesn't tell developers or publishers how much their games are worth. They only provide the tools for them to sell them, and they obliviously get a cut from it, but only if you sell. They don't ask for money in advance, they don't ask for any contract.
Valve is a store front, not a publisher. I'm thinking you are just confused about how they operate.
They already are.
I really think you know nothing about what you talk or how the market works, this isn't even fun.