That's the natural condition of a theoretical free market, real markets are not theoretical. As Keynes said, the market can stay irrational longer than you can stay solvent.
Also, poor people have more children than rich people.
They very often aren't, that's true. And in many cases, that's because real markets are not free markets; they are skewed by government intervention. The market for labor in the US, and indeed in most countries, certainly fits that description.
> As Keynes said, the market can stay irrational longer than you can stay solvent.
Yes, and he did his level best to make that prophecy come true by getting governments to intervene to keep markets irrational.
> poor people have more children than rich people
How is this relevant?
A million things skew the labor market away from the theoretical: people are irrational, information is wildly asymmetric, wages are sticky, there aren't an "arbitrarily large number of firms", the factors of labor (people) aren't liquid or mobile, etc.
To pick 'price floor' from the long list of things that distort the labor market while ignoring the rest is strange enough that I chalk it up to politics any time I hear it.