I'd argue the better analysis is that employers set their salary floor at "single person, 2 kids" and let the people with more cost-effective situations benefit

I'd argue the better analysis is that employers set their salary floor at "single person, 2 kids" and let the people with more cost-effective situations benefit. This also means that the employee who wants a big family is faced with a greater financial burden. That makes sense to me. Speaking only for myself, I have several coworkers who make the same salary as me, but have zero children. I sometimes envy their lifestyle, but I don't begrudge the fact that they made a more financially advantageous decision than me. It is true that some employers will preferentially mete out promotions and vacation based on family status (having a family is famously a career advantage for men, but not for women, although spending time with said family is universally a career disadvantage), and this is discrimination.