Left to our own devices, some of us guesstimated how much the parents of the bride spent per person on dinner, and gave a somewhat equivalent amount per person. As a consequence, the scale's been stuck at $100 for decades.
No matter that today that same dinner costs $250 per person, or that the couple may be paying for the wedding themselves. Or that this is his second wedding and her third so maybe they shouldn't be getting gifts at all (at least not from you again).
Some wedding guests base their gift-giving on moral judgments - such as whether they approve of the couple's lifestyle and career choices. They then give less to couples who shack up before marriage, more to virgins and future heart specialists, and stiff caricaturists altogether.
Faced with an invitation to a graduation party, these individuals undoubtedly determined the amount of their gift on the basis of how well the student performed (4.0 GPA vs. 2.5) given the degree of difficulty (physics vs. pottery majors) and the reputation of the institution (Harvard vs. Slippery Rock).
Temple University psychologist Frank Farley has been teaching for 38 years and he thinks you should write as big a check to the college graduate as you can.
"The motive should be the need" of the graduate, he says. And he worries most about those getting baccalaureates as their final degrees.
Maybe the B.A. should get a bigger cash gift because a bachelor's degree doesn't open as many doors in the job market as swiftly as a law degree or an MBA. But it definitely doesn't seem fair to Farley to give more to a med school grad, as some people argue.
The med school grad may have more loans to repay, Farley says, "but he or she may soon be one of the highest paid people in America."
As for the state school vs. Ivy League, Farley says the gift-giver might want to know whether the parents paid the tuition or the student is left with looming loans.
Shelley Nohowel, in sales at Jeffrey Miller Catering in Doylestown, prefers to start with a level amount, $100 for an undergraduate degree, and build from there "if you've got details. For example, I know a divorced woman who borrowed up the wazoo to go to vet school."
That kind of effort, she thinks, deserves a reward.
As for how much to give the newlyweds, don't bother looking for advice in one of the overpriced wedding-etiquette books that line the bookstore shelves. They advise only when to write the thank-you notes. (No time like the present.)
Etiquette does allow a year for your wedding gift to arrive, according to the books, but postponing the inevitable only lengthens your to-do list.
Let's go back to Nohowel. She favors a wedding gift in an amount based on the couple's costs: "If you know the wedding at the Four Seasons cost $150 a head," she says, "I would give them $300."
Thank goodness she is pretty much alone in thinking "$100 is just not enough of a gift for a wedding in today's economy."
More folks seemed to agree with wedding planner Sarah Doheny, who says "$100 is perfectly acceptable and couples should be grateful to get it."
Rosie Amodio, executive editor at The Knot, a wedding Web site and magazine, says a reader poll showed that brides and grooms expect to get between $50 and $100 from their guests. "So we advise at least $50," Amodio says. "The idea of paying for your dinner is an old notion. Today's dinners make that too expensive - especially if you're traveling to the wedding and have to pay airfare."
Does it matter if you're not even that close to the couple? And what if the groom is the son of a business associate? Can you give more and hope to get some payback?
Giving should never be manipulative, says etiquette expert Mary Mitchell.
So don't bother giving lavishly to your business associates' children, says Doheny, because "there's no guarantee they'll ever find out how much you gave."
It's worth mentioning that the happy couple and their overburdened parents should not try to recoup the wedding expenses with gifts of cash or goods.
"The reciprocation game is a sticky wicket," says Philadelphia-area wedding planner Melissa Brannon.
And she adds what is perhaps the best common-sense advice: If you're going to be cheap, plan ahead.
Yes, the ideal way to give a lovely, less expensive gift is to select something from the couple's registry and include a personal note.
Or, stop at Lowe's or Home Depot on the way to the wedding and buy a $100 gift card. Surprisingly, says Diane Forden of Bridal Guide magazine, that looks less cheap than a $100 check.
And never give cash - it might get lost.
Contact staff writer Dianna Marder at 215-854-4211 or by e-mail at firstname.lastname@example.org. Read her recent work at http://go.philly.com/diannamarder.