Replacements don’t have to be equal in transfer fees and wages. That’s what many of the fan base don’t get. When we sold the likes Hughes, Ince, Kanchelkis etc we replaced them with class of 92. No fee, and initially on lower wages. When we sold Beckham, Heinz, RVN, we replaced them with players who were on lower wages. And many of whom took a year or more to really shine. Eg Ronaldo only became WC at United in 2006. Then in time the players earn the right to increase their wages and guess what? They spend 1-2 years as top earners before being sold on and the cycle continues. Obviously Ronaldo being sold at 24 was not part of the plan.
Real Madrid sold Ronaldo for £100m and replaced him with Júnior for £45m. Should be stated for a few years many RM fans thought he was crap. They signed Milto before selling Varane, he cost £50m but likely he was on lower wages. Same with their cdm rebuild.
The point is you replace stars just as they start their decline. Ideally at the time when the media, pundits and many fans can’t see it and think it’s a mistakes.