When we talk about resale value we are aiming to get a player for a net cost of at most zero. That means we are actually looking for players whose value will INCREASE within a few years and then we can literally engineer a sale at a higher price, recouping his wages on the way.
Even Kone comes at 5M this year and leaves 10 years later (while still performing at an acceptable level), we are still losing ~15m over 10 years, not counting inflation.
(assuming he costs us 1m/year in wages, bonuses and various fees, which translate to ~15k-20k/week)