Didn’t see it listed in the other post but the last steam sale was $53.97 so this is the best price so far for the game.
Edit: thanks for the correction.
you get the coupon by either claiming (as opposed to downloading) GTA V or you can just claim the first coupon by itself.
After that, with each eligible purchase you get another one automatically.
The coupon is not dependent on either downloading or making many purchases.
Due to currency inaccuracies, some people are getting this for $10 :(