I have friends who have spreadsheets from their wedding reception and consult it before purchasing a gift for their friends.
"Oh, Susie only gave us $200 for our wedding. She gets $20 for her birthday."
Sometimes, they pull it out to make fun of people.
"Aunt Mildred only gave us $150!! Can you imagine?? I hope she enjoyed the food the free-loading jerk."
I'm not kidding. These people are no longer my friends.
They also subscribe to the "cover your plate" rule, which I find asinine at best and downright repugnantly rude at worst. If you can't afford your damn wedding, then have a cheaper one. I don't exist to help pay for it. I exist to help you celebrate it and offer you a token of my appreciation of your invitation and wish you well on your future life. And I'll express it however I please. If it's in the form of a $100 check that you find distasteful, I'll happily take it back and assume you're an assjerk for the rest of my life.