Okay, I'm a little confused here.
The party was held at B's house and beforehand, A suggested that everyone chip in money for food and drinks and such. (This was not even B's suggestion.) I assume A suggested this because A was hoping the party could be held at B's place but because B hadn't volunteered, A didn't want B to feel unduly obligated ("voluntold" as I have seen it said here in this forum).
The money was collected, and used by someone (the original post does not even say it was B, or if A used it) to obtain/reimburse for the supplies. B did not get any money for hosting. No profit was turned. The money went to the party supplies.
I'm confused as to why anyone would be offended, particularly specifically at B. If you'd all gotten together at a local park or something, and everyone chipped in for supplies, would that have been rude? If "potluck" type parties are not your cup of tea, if you only like fully hosted ones, well, that's your preference and you don't have to go, but to find them offensive is just really odd to me.