Calculate the cash adjustment from two consistent values

The basic calculation is simple: compare the agreed values of the two items and assign the difference to the party receiving the higher-value item.

The difficult part is not the subtraction but which values to use.

If one item is valued at a realistic selling price and the other at the highest asking price found online, the cash adjustment is biased from the start.

Before agreeing the final amount, agree on the method: realistic market value, trade value or another explicit reference.