I never heard about the dreaded “cover your plate” theory till I moved from Florida to NJ.
My family is from the south - NC - and actually $$$ used to only be given by close family. Gifts were more common from friends.
“Cover the plate” is crass to me as well; invite people to a party with the expectation they’ll pay for it is not very polite.
I give what I can afford; if I know the couple extremely well, I will pick out a personal gift.
VCNJ~