Yeah, as others said, I didn't really get it at first, but when I spent some time with it, I eventually got it, and the game is pretty fun. A tutorial, or even a description of the gameplay on the store page would be very helpful.
I also love the way you incorporated the theme in the gameplay of buying/selling items, and how you cant attack unless you sell. Everything really does have a cost.
The visuals of the items themselves were great, and the sound design was nice!
My best run lasted until level 52. Fun game!