[runako]

Correct. You are on the hook for 1x, not 20x, your down payment. This is asymmetric leverage in favor of the buyer.

[shapefrog]

It is a fair point that for small negative changes you are getting a leverage effect (i.e. for a 1% down move in asset value you do have a 20% loss on your capital).

There is however a floor so the payout profile is a lot more like an option.