We could simply match the offer they're getting from somewhere else and save them all the hassle of completing deals.
Let's say Juventus offer £45m for Reguilon, so Madrid exercise their £(28+15)m, buy back clause to make a £2m profit. We could simply pay them those £2m and keep Reguilon and change his original cost from £28m to £30m.
If Juve offer £50m, then we pay Madrid £7m and change his cost to £35m. Whatever offer another club makes to Madrid, we can actually 'match' it by offering £43m less than that! Sounds mad but the math checks out!
We'll only really come unstuck if Madrid sack Zidane and the new manager sees Reguilon as their starter.