For more context on "very expensive," a MuJoCo license was several hundreds of dollars.
Isn't that the whole idea behind college? Spend money to learn cool stuff?
Sure. But who argued for that? They merely pointed out that they considered this particular physics engine worth spending money on. The implication was that because money is typically limited for a college student, the software must really be worthwhile. The implication was not "LOL, you must be broke and can't afford good software."
TLDR: personal non commercial 500$/year for usage on up to 3 computers personal commercial 2000$/year