Only 4 days? Man, you guys are indeed spoiled if you think that's alot. XD
4 days is nothing to go from faction to faction and get the Dragon King set.
It sure beats paying to have everything unlocked, imo.
On top of that, you can wager in the Krypt and get more coins that way as well.
Again, though, it's just cosmetic stuff.
If it was having to go through a Krypt-like system for upgrades that affect actual gameplay in Injustice 2, then I get that and I agree that that's a no-no.