It is a RNG event, so it is possible for you to get more or less points. You also get less points on the first 2 trees. The price is based off the level 3 tree, which is around where you end up at the end of the week after all the free spins. If you missed any free spins and are still on level 1 or 2 tree, then It could cost you more. Mathematically it could cost you anywhere from 540 coupons to 108 coupons or less. But you are at the whims of the Random Number Generator.