Let’s unpack this a little. I think there are various ‘channels’ within the hookup culture, and I’ll list just two that I think stand out:
1. The contractual approach: basically prostitution. Quite often when men travel to 3rd world countries for sex, it’s for very low cost sex in exchange for money.
2. The mutually motivated approach: I liken this to friends with benefits, where the exchange of value is non-obligatory or transactional, and based more on reciprocity.

Now I personally don’t see anything intrinsically immoral with prostitution involving consenting adults. I do think however that one can despise the prostitution hookup while indulging in friends with benefits.