I have no idea what level you are at ,but I would suggest that the keys in particular, are no different than many other items that are required for later stages in the game,and which generally are hard to come by,at least for few,some,many players,where others seem to be able to zoom through the levels once a new feature appears.
There is definitely better offers for certain players.
I dont know how easy they are to come by in the normal game if you have the abilty to kill ubers effectively, or get a chest from the level 8 and 9 tiles.
They are also available to "win" in the new quests,but only if you manage to get to the higher levels,and especially so if you pay the extra fee ..