I’m conflicted on this. I’m jaded because I come from a family and my girlfriend comes from a family who are constantly looking for ways to trick/guilt others into paying for everything for them, so I took this as a situation where they’re going to bring this up so OP actually does feel obligated to pay. And it’s unlikely they’ll say no when he does offer.

When I graduated from college and got a decent job, my girlfriends family got increasingly entitled in similar ways to this except I choose to stand up for myself.

The difference is though, they’ve never spent any money on me so they couldn’t hold that against me like they could OP.