Wow, great responses, and good advice. Echoes what we were thinking in general, and I guess we feel better knowing that we're not the ones who are out of line. And I love that Yoda graphic!
I'd like to respond all around, but I'm at work. So, in brief, we are not assuming that nobody else on the invite list agrees with us. I think the comment that the hostess is trying to score points with H and B is bang-on, we've been noticing that they seem to inspire some degree of 'devotion' from certain people! They're charismatic like that. We hadn't noticed it before last fall, but in retrospect, it was always there.
Initially we gave H&B the benefit of the doubt that they didn't know what the Hostess was doing, but my impression was that it was B. who suggested the Bank Machine Map. In truth, I think H. probably doesn't know how far it has gone, and if I told him we were offended, he'd be very apologetic.
I know we shouldn't go, but the rubbernecker and the pragmatist in me are battling it out. I want to see how thoroughly they can mock etiquette and taste, but at the same time, I know I'll have to negotiate a maze of donation jars, money-taking games, gentle pressure and guilt trips. But we have well-developed guiltproof armour :-)
Also complicating matters is that we are the outsiders in this town. The invitee list represents many of the friends we've made here, plus many of those same people attended a pre-wedding event for us last year which had a fundraising element (which we were uncomfortable with). I might argue that attending long enough to give our best wishes, then leaving, might be the best high-moral ground action to take. Although we've been working to expand our social network outside this group over the past year, we'd rather not be the subject of snide comments behind our back, justified or not, or thought of as ungrateful.
If we decide to go, we will give neither money nor explanations. "sorry, we're stretched a bit thin this week" is the most we'll say. I might add that our cash-gift budget is reserved for the two weddings we've been invited to this summer.
I have heard of "bon voyage" parties, but they are usually mostly family events, and usually the vacationer is going for an extended trip... long enough that people would notice they had gone, at least!