While this is true, this would represent a profit on the books, but from a business perspective its a net loss as you've made less on an asset than you paid forI’m not sure that the original purchase price has such a direct bearing on a sale price.
It’s standard practice to take a players total cost and annualise it in the books.
So that a player costing say €120M on a 5 year contract would be valued on the books at €96M after 1 year, €72M after 2 years and so on until the book value is (obviously) at €0M after 5 years.
I think Felix will have been at AM for 2 years now so €72M + €1 would show as a €1 profit in AM’s accounts.
So on the books Atletico would be happy but in terms of cash flow they'd be making a huge loss
That also doesn't include his huge €250k a week wages that he hasn't been worth, I'm sure any club who wants to buy him would probably offer him less, so Atletico may have to pay him off in some way