Hey man, i've got a simple idea, just add more Ingots, and make some new weapons with it, and maybe you can mix different ingots for the same weapon and stuff, and make the ingots more expensive, in 7 days i've got 20k
When it comes to profit margins and how fast you can make money, it seems like everyone has a different expectation of how fast they should progress. I'd recommend using some kind of difficulty setting that would slow down or speed up the accumulation of money. This way everyone could enjoy the game at their own pace.