Use the player's organs/senses as currency or bets - if they do not wish to buy items with HP, especially if it is a powerful item, they can use their organs/senses. For example, if they want a really powerful weapon, they can sell their left eye - as a cost, the left side of the screen will go black. The more powerful the item may be, the more organs/more important organs will be the cost.
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Losing liver = poison effects last longer, screen tint yellow
Losing heart = highest value, leaves on 1HP
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