Not sure about the wax part, but Magic Clay is available for about $20
at Pep Boys and is extremely useful for rubbing on your dirty paint to
remove virtually all deposits harmlessly leaving a paint surface as
smooth as a new born's a.s. The car needs to be washed prior to using
it. Of course after using it, would be a perfect time to apply a wax to
the now clean and smooth surface.
Stan K.

if you are not familar with magic  clay: it comes in t box (its a hunk
of clay and they also have a bottle of liquid(probably an oil) you take
out the clay and rub it on the moisted car surface to get out all the
stuff the car wash did not get out.. on one of our cars it looked like
very tiny dots of dirt on the surface that would not move with water and
soap..... rub the clay back and forth and the spots come off......
its alot of work and if they are charging that price it might be work it
if its needed and you dont want to do it....