It seems some balancing is in order to prevent the player from betting too low, while still keeping them from losing so much money from low bets. It doesn't feel like how a real slot machine would run at all. Perhaps the bet should be the same every time? There are a number of ways you could fix it, but at the current moment, the main mechanic, betting and getting a return, doesn't work how most people want it to. Vibes are cool.