Does that mean that when I remodel my house, I would have to negotiate on time and materials terms, lest the contractor accidentally underbid and end up with less than minimum wage?
I think the law rightfully distinguishes between truly negotiable contracts and take-it-or-leave-it terms offered by a party with more negotiating power.
Of course not. The prices someone sets are not related to the wages they're paid. You're paying a price; you're not paying a wage. The contractors are paid a wage by the business owner; if he pays them less than minimum wage it's illegal; if he pays them more, but does not recoup that cost on the job because he underbid it, that's a business loss.
Why do we treat these things differently? Why is the GC permitted to make bad business decisions and earn below minimum wage, but the people he employs are not?
I think the law rightfully distinguishes between truly negotiable contracts and take-it-or-leave-it terms offered by a party with more negotiating power.