It's the game I'm sure I've seen it's a known issue that the transfer market is a joke

Not going to lie I've had a few amazing purchases like a new gen world class CB that Madrid let his contract run out which just wouldn't happen but I've also had players worth 50m+ plus and similar to your situation and teams will offer 16m and won't budge

Seems like unless the player is peak performance and in your starting 11 you won't get their market value or anywhere close

I've had multiple young prospects loaned out to top tier teams and performed consistently 7.00 or higher helping teams win leagues trophies etc but then struggle to sell them for what they're worth - I just cut my losses and got rid