This is a clicker game that actually made me play it through in one go (took approx two hours, all I can do now is level up the worker´s speed/duration.)
However, I agree to the fact that the prices should be balanced a bit better (see below comments, gold = silver etc.).
--> Bonus waggons: They brought me too much income too soon, so I had the diamond, silver and gold mine before having the achievements for the other mines, and so I produced only jewelry. As long as you do not have the respective mine, if you get items from the bonus waggon you did not find/produce before, they should change to the highest value item you already got/produced instead - or their quantity should be only 1 - 5 instead of 150.
--> How about an "item value change": every 10 items of the same kind you sell within 5 minutes decrease the $ value for that item by 1 $, until a certain minimum $ price is reached. 3 minutes without selling increase the price again by 1 $, until a certain maximum price is reached. This way, the miner would have to actually select which goods he wants to sell at which time.
--> "Level up" for crafting items: I would add a percentage that crafting an item can fail. The more often you craft that item, the more experience/skill you gain in crafting it, and the "fail" percentage will decrease with this experience.
--> "Sale amount control": what is rather disturbing is that you have to sell everything yourself by clicking 1 by 1. Once the player reaches a certain breakpoint (you could use the achievements for this!), each click should sell 2 / 3 / 4 / 5 / <enter number> items per click. ("enter number" = the player can put the amount, see the price and press "confirm" to sell all at once)
--> "Worker model": Ok, he is a mouse cursor. Why not give him a skin instead, like an actual worker? Actually, you could try to combine the high resolution background with a "pixel art" worker. Leveling up the worker could give him new tools or pickaxes in new colour, different boots (speed update) etc..
--> "Background change": depending on the mine you enter, a different background - or the same background but in a different colour pallette - should be shown (bit less boredom - "I want to see which background comes next so I keep on playing!").
Issue found: The green bonus waggon: When clicking it, the game slows down a LOT, until the menu that opens up to show which bonus you got, disappears or is closed with the "X".
This is all for now, keep up the good work!