The windowcard prices are highly variable, as one might expect. Each show sets its own price. Several shows have sold them for at least $200 (the big musical with all the buzz or the play with the big movie star). I believe A Steady Rain was $350. I saw Natasha, Pierre, and I think their smaller-sized-poster was $10. $75 or $100 is a pretty common price point for a new musical. Long-running shows charge less, and most plays do, too.
"What was the name of that cheese that I like?"
"you can't run away forever...but there's nothing wrong with getting a good head start"
"well I hope and I pray, that maybe someday, you'll walk in the room with my heart"