How much does a wing cost? We've seen them for about $250-$580, painted and with a complete installation.
Even though the wing is mostly a cosmetic item, at speeds over 60 MPH it actually makes a "slight "difference in performance. Because the wing is usually not adjustable, it's not too useful in a racing situation.
What a rear wing is supposed to do is keep the rear end down in quick high speed turns (at the expense of a getting little more wind drag).
Many people crash on freeways when they cut someone off at 80 MPH with a "quick" turn... they spin out. A wing aids in keeping the rear end down at high speeds. Unless you're making quick "snap turns" at over 80 MPH, the wing issue is purely cosmetic.