Wiktionary
there's no such thing as a free lunch
prov. Nothing is free; even things that appear free often have to be paid in the end.
Usage examples of "there's no such thing as a free lunch".
Behind the desk were more signs, most expressing some negative concept (IF YOU DON'T LIKE OUR TOWN LOOK FOR A TIMETABLE, DON'T SEND A BOY TO DO A MAN'S JOB, THERE'S NO SUCH THING AS A FREE LUNCH, NO CHECKS ACCEPTED, NO CREDIT, CRYING TOWELS ARE NOT PROVIDED BY THE MANAGEMENT) and a big red button marked POLICE CALL.
I shouldn't have to tell you this, but there's no such thing as a free lunch.