I think recently they gave good offer to buy from units and insisted us to but it from real money becuase they are not going to give units from battle chips. They added two 4* basic arena there we had good chances to get units from milestones as well as from battle chips. So to maitain financial stability in game they reduced but now only one 4* arena is there they must increase the chances of units from battle chips.
Noone should open them now bc there will be a +20% gold event in december. Also RNG is a thing
@AshKetchum you proved it. This is very less. You got units in only 2 crystals.