Logit/Probit with numbers different than 0 or 1?
I don't see how Logit/Probit models are relevant here. They are designed to estimate conditional probabilities, not what you describe.
It appears you postulate a relation
$$S = f(P, C)$$
namely supply being a function of price and cost, and where you treat price as a &quot;control&quot; This could be written as a linear regression model, as a first-order approximation. Why don't you think estimating that model?