I'm a little put off by people telling me it's rude to think you need to cover your plate. These people are the very same supposedly polite "southern ladies" who introduced the idea of bridal registries to middle class Philadelphians and New Yorkers. Even 20 years ago, my wife and I had never even heard of them. And the first time we saw a registry, we were appalled that people would tell us what to buy them. (Here, although registries have become common, most couples still only register for showers, not the wedding).
All that said, there are a few people who don't need to worry about covering their plate at a wedding - the parents and grandparents of the couple and other very close friends and family. If they can't afford it, they absolutely should still attend. Otherwise, work people, not close aunts, uncles, and cousins should stay away if they can't afford it.
The way I see it, a wedding reception is a social occasion to mark a sacramental event. Here in the northeast, while eloping would be fine for a career, announcing a Church wedding date and not inviting the office could very well be career suicide.
As Catholic parents, we wanted nothing more than our children to be married in the Church. We realized the burden this planned and announced date put on our children and sometimes on their in laws. This is why we have always paid as much toward our children's receptions as we could. Of our 8 married children, I would say only one couple had very specific ideas about their reception. The rest were just trying to do what was socially acceptable.
And here that means a cocktail hour, an open bar throughout dinner, and at least a DJ. And if you're an attorney with massive student loans, a VFW wedding with a keg of beer and hot roast beef might be what's in the budget, but it'll hurt you in your quest for partner. And so, I maintain that here in the northeast it would be rude to be on the periphery of the couple's circle and to attend their wedding without covering the cost of your plate.
Like others on this thread, my husband and I preferred a small and modest wedding we could afford to a big costly one we couldn’t afford. We were adults so we didn’t ask our parents for financial help, either—we considered it quite enough that they had to travel to the area where we were living. Still, the ceremony was beautiful and memorable, the only one to be held in that particular venue (and the venue was free!) We invited people we loved, and were glad to pay for their food and drink. And having a small but charming wedding did nothing to harm my husband’s ascent up the ladder in his profession.
The gift registries aren’t intended to be a way of telling guests what they have to buy. They’re supposed to save embarrassment for everyone. So if Tilly and Vortigern are getting married and you can’t spend much, you don’t have to call up Tilly’s mother and hear her tell you that Tilly and Vortigern need twelve thousand-dollar Flora Danica dinner plates. You can just look at what they have on their registry and find something that’s at the price point you’re comfortable with, from a bath towel on up. You don’t have to buy a gift from the registry at all, if something else catches your eye. Or if you don’t want to buy anything at all.
I guess traditions are different in different parts of the US. We can surely accept each other’s traditions, and I will remember never to accept a wedding invitation from Italian-Americans in the Northeast, because I truly could not afford to give an acceptable gift these days. But surely we’re all in agreement that pitching a fit if someone doesn’t give you enough money is vulgar, yes?