At the next promotion, make a box as you are so oft to do, with whatever probability distribution works.
Then, price the items inside of the box appropriately and put them all up for sale directly. For instance-
New prize box! 5 dollars.
Prize box as usual.
Bad prize (that 70-80%): 2.45 USD
Most of the sarongs/trunks were being sold for around this much, but in crowns
Moderate prize (The 20% reskined weapon): 20 USD
Charcoal grills, forks, etc. were all being sold for around 500K crowns.
Price varied, but felt like about the average, if not too low.
Good prize (if at 1%): 100 USD
As if the player had just purchased the 100 dollar energy bundle and traded it for the big item.
This might actually be a bit of a lowball on most of these things, to be honest.
Perhaps selling the items alone in the supply depot or simply for real world money would make you a larger profit? It would still be some good data to check and see.
I think they already did that in the last promo, in which they sold the boxes separately.