When I was at school we used our own pocket money to buy something small. Eg a single (am old!), something little from
The body shop.
Oldest DS is now 15 and while organised parties at venues have stoppped they’re starting to organise get togethers at each other’s houses. Nothing rowdy, just maybe a trip to 5 a side then pizza or takeaway afterwards. We give him spending money for all of it unless parents are specifically paying for some part of it eg pitch hire or escape room entry, in which case we give him just enough money to cover his share of food/drink etc
Because it’s not a formal party at a venue thing like when they were younger at soft play or trampling DS doesn’t think he has to even give a birthday card at these things. Says that boys don’t do that!