There has recently been a slight change to prices.
Gambler’s Boxes are now 900k GC or 900 BC.
Legendary Boxes are now 5k BC and 95k BC for 20
Explosion Crates are now 400 BC and 75k BC for 200

First, it computes a multiplier based on the highest level you have reached on any ascension. If this is not 9001, the multiplier is (bestLevel / 100) rounded up. If you’ve reached 9001, it’s 100.

Green Coin gain is 50k times the multiplier.

Blue Coin gain is 50 times the multiplier.

Arena EXP gain is 50k times the multiplier, except when you are doing a rebirth and haven’t finished (then it’s 0)

I didn’t know it was based on the highest level instead of the current level. So I will stop to not let myself use these crates before reaching 9001 during any ascension anymore, but I will not use them now because of v1642.

So if best level is 9001, we get :
5,000,000 GC
5,000 BC
5,000,000 AEXP
25,000,000 pixels
5,000,000 CM

Just going to leave this here: the average Insta-Progress gained from Progress Boxes is 18.56295. Might help if you’re interested in the boxes and wish to calculated whether or not they’re the best choice.