As a member of a group who use supplemental oxygen, that extra $75 for the cat looks puny!
While the situation is improving, slowly, it has been common for folks to buy an airline ticket for, say, $100 each way, even with a change somewhere along the way.
Getting oxygen service from most airlines was up to $100 per segment. That translates to $400 on a round-trip ticket. Under the foregoing scenario:
Person = $200 roundtrip
Oxygen = $400 roundtrip
and, the cat or even the oxygen equipment would take up so much less room than the human! Ah, well, it revolves around a government program, so you and I both know that there'll be something majorly wrong!
SWR