It is a casino, you are pretty much gambling.

Kinda wished that they would give us the average value of items on it but I know many players would dispute the given average value because we have the variable price fair and various other methods of acquiring coins, credits, chips, hero cards, medals, etc. BTW Tynon probably uses jewelry salesman prices for the value of chips.

What likely happens is that lottery chests are set to be given out at 75% of the time (probably not the actual programmed value i just made that number up) With various other tier like uncommon, rare, ultra rare, and "so rare that players will be lucky to see a WC message for it in a year of playing and they shouldn't even hope that they will it themselves."