Okay, let's look at this logically. So far, we can say, with certainty, the following:
1) The page explicitly states you will get a value exceeding what you paid.
2) KPscore is the cost for a bronze box, ergo, you ARE using it to pay and it MUST have SOME value.
3) The value of 10 KPscore is obviously less than 60, violating #1.
4) There is no objective way to translate the value of 60 KPscore into something else since it can't directly purchase anything and is not otherwise attached to any item or monetary payment system.
5) Making the award more KPscore than you spent is pointless since it would just allow infinite tries.
Looking at this, #4 can be relevant multiple ways. Since you can't get anything directly with KPscore, it's also hard to argue that any amount of something that you CAN purchase things with would be worth more. Even a single gold or honor medal holds more intrinsic value, yet it still takes a lot (189 honor or 180 gold) to even get the cheapest items from the stores. So, it would still take a large number of tries to get enough to buy something.
Of course, there is also another avenue: 1000 credits/points. It's worth less than 1 gold (the 1 mil credit/point packs in the store amount to just about 2800 per gold), and I currently see that item about 1 out of every 3-4 tries on the Fortune Wheel. Each try for the Wheel is 30 KPscore, or about 90-120 per item if you look at it that way. So again, it's hard to argue that spending 60 on a box that guarantees at least that much doesn't get you more than your "money's" worth.
Excellent options for bottom reward, instead of KPscore, include 1 gold and/or honor medal, or a 1000 credit/point item. All of these are easily argued to be worth more than 60 KPscore, but at the same time are not particularly valuable except in very large quantities.