Crab crediting is the act of trading crab (or other expensive meals and delicacies) for sexual favors.
"I heard Dave is a sugar daddy."
"Nah, he just does a lot of crab crediting to get what he wants."
"Oh, well, I guess a girl has to eat!"
"Jane, you stupid filthy slut, I heard you've been crab crediting at the local Red Lobster again."
"Hey, a girl has to eat!"