He didn't make an investment in their evening. All expenses were paid by Mommy.
Okay, I see that ... but do you think the teens involved see it that way?
After 20 seconds of explanation from their parents? Definitely.
"Lisa, I'm sure you're savvy enough to realize that Joey is a nice kid, but he doesn't make enough money to cover even the cost of the Prom tickets, let alone all these other goodies. His mother is the one who did all the work to earn the money to send you, Joey, and the two other girls in your crew. Make sure you thank her and show your appreciation, because she definitely didn't have to set up such a nice treat for you and she's being very generous."
The three young women, meanwhile, might not necessarily have thought of it as a "date" regardless of who paid since it's increasingly common for people to go to proms in groups of three or four.
That's true, but somehow I think an over-indulged kid like this would consider each girl a "real date". Can't know for sure.
He might consider things however he wishes. But if his dates don't, he's outnumbered three to one and out of luck unless Mommy also sprang for roofies.