Re tax money or indirect subsidy (higher ticket price) -- Absolutely true. Why is this an issue? Because the federal government has taken upon itself the obligation of protecting us from ourselves.

Either:
A) let us decide our own risk to ourselves and immediate family members
B) forcibly reduce risk, which requires the "help" of everyone else

Requiring infant seats on aircraft, but not free, is neither A) nor B). It isn't B) (despite being compulsory), because risk is not being reduced.