curious do you guys usually buy the cheapest boxes or the more expensive ones?

Depends on why I'm buying. If I'm doing drills quests I just buy the cheapest. If I'm looking to acquire specific items, I work out the value based on user price (not going to pull from the mystery box for 15000 sP when I can buy it in user shops for 5000 sP), and will usually buy up to 3x the shop price.

When a super expensive item comes up, I usually avoid it - I know its going to be a retired item, but every single time I've given in to temptation to buy it, the value of the item (retired or not) has never been above the price I paid, so not worth it.

ooh ok thats interesting because i have been trying to figure out if the higher price boxes are worth it and so far it seems they arent