Share your insights or perspective on the financial matter presented in the input.

What is the opposite of a sunk cost? A “sunk gain”?
In the second example you are giving up future  free cash flows in exchange for a capital gain on the original investment. With that respect  the money you will not gain will be the difference of the future cash flows ( net of related costs) minus the net gain on the panel you have sold. The financial result can be considered as the opposite of a sunk cost, that is a cost you have already incurred ( and cannot be recovered)  vs net future gains you are giving up.  In more sophisticated financial terms we are talking about the  benefit-cost ratio:  ( from Investopedia)