I think they are just selling at the top of what they think he will be worth; Cucurella is turning 28 this summer. He's not going to be going up in value in all probability. They aren't getting quite what they paid back, but it's pretty close and even getting close looked very unlikely for a good while there.
Edit: And the point that this doesn't make them better is very true. But they've committed to this model where they have to sell players to recoup the fees so it is what it is. They can't really afford to keep an "asset" that will be depreciating rather than appreciating. Especially since they've overpaid. And the Mudryk transfer looks like it will be a near total loss even if they eventually get a little back.
Edit: And the point that this doesn't make them better is very true. But they've committed to this model where they have to sell players to recoup the fees so it is what it is. They can't really afford to keep an "asset" that will be depreciating rather than appreciating. Especially since they've overpaid. And the Mudryk transfer looks like it will be a near total loss even if they eventually get a little back.