Here's how it works:
You and I determine the value - compared to other sales.
We agree on a minimum "guaranteed price" that it will sell.
If it sells for less than the "guaranteed price," I pay you the difference.*
For example, If the "guaranteed price" is $1 mil. It sells for $980K. I will pay you $20K.*
It sells for $1,050,000. You keep all YOUR PROFIT.
You have no downside because I pay you if it sells for less. If it sells for more, you keep all the additional profit.