Are “lb” or “lbs” ever pronounced differently from “pound(s)”?
This is the only instance I have ever heard of, of someone pronouncing "lbs." as something other than "pounds." Since it's intended as a joke on Lucy's naive understanding, I'd say it's clear enough: few do this even as slang, except as a joke or a mistake. (And if it weren't for Kit's comment above, I'd say "nobody.")