Of course you don't tell people they have to pay mid party. This is for things like collecting donations money for next parties.

In places when you don't have a lot of money to go around, solidarity goes a long way, and nobody finds it weird to ask for help.

I understand on HN the average salary allows to pay for a lot, but it's an exception.

In France, it's common that everybody brings something for dinner, for example, even if you are invited.

If you throw a big party and then ask people if they want to help the people that did that, they are usually happy to do it.