Difficult to bring back and re-sell after a season looking decent in Segunda. This isn't England and the Championship unfortunately.
A comparison would be Cuenca. Sold to Villarreal from B in 2020 for a few million. Had a couple of LaLiga loans, played 500 minutes for Villarreal this season. But if Villarreal were to sell him today, they would probably struggle to get more than the 2.5 they paid. And then there were 3 seasons of wages on the books more or less to account for.
So a good decision for us to let go back then.
As 983 said at the top of the page, the whole of Spanish football is financially broken.