Well to me, when I am invited to someone's home for a birthday party, I think Cake, ice cream, hot dogs, chips etc.. followed by presenting and opening gifts, and then you go home. If you are invited to a club for instance, where you are told in advance that there will be additional costs besides a gift, (cover charge, drinks, valet, coat check, AND food) you may be spending around $200 PLUS buying a gift. With advance notice, you can decide to go, or not to go, depending on your circumstances. When you go to someone's home for dinner, you shouldn't have to expect a BILL for doing attending. As far as I am concerned, when we host, we HOST. That means that my husband and I are paying for everything. We don't ask anything of our guests, but for them to come and join us. I wouldn't dream of ever charging guests to come to ANYTHING we are having, even if it were at a club or restaurant. It's OUR party, and WE absorb all costs associated with it.
As far as the birthday parties at clubs and such, we didn't "pay" to "attend" other people's "birthday" parties growing up, and to me, it is just classless to have an event, and expect the guests to pay for the privilege of being there. Of course with advance notice, those who don't MIND, are free to do so, and evidently have no problem with, so more power to them. We just don't attend parties like that. If we are just joining a group of friends who just happen to be going to a bar, then of course we pay for our own consumption, because there is no "featured" guest. I hope that is a little clearer.