free to play, with no gameplay restrictions is an excellent model. when you can then do IAP to get "extras", it's a great "pay what you feel it is worth" type model.
another mobile game, Vainglory, does this with currency to unlock heros and skins. you can play the game to earn currency to get them, or just purchase outright.
Also works well in CS:GO. The skins add nothing to the actual game play, yet people like the value they add. Just a shame that it brings kids into a gambling state of mind. Would've been nicer if you could just buy them outright.
You can, it's an actual market. The price is just high, because the chance to get them is low. If you could buy them for what I assume you expect to be a lower amount, they would not sell nearly as many chests, or no one would want the item anymore because it's no longer rare.
another mobile game, Vainglory, does this with currency to unlock heros and skins. you can play the game to earn currency to get them, or just purchase outright.