Genuine question, why is this now becoming a thing with signings?
Is it due to the increase in wages? Go back a couple of years and a £50 million player was a £50 million player, now there's this push to include wages in any talk of a new signing to inflate the appearance of the cost of the signing, wages have always been a part of buying a player. It started as a way to insist opposition sides were overspending on players (sometimes very true) but now it's used for anyone young with big potential. Where are the figures for Tchouameni from and what are they based on? From what is often reported for targets, short of very few players whos demands are clearly outlined before they're bought (correct me if i'm wrong) most players wages, the agent fee etc are never really brought up which seems to suggest these package discussions would be filled with wild speculation based on little factual information unless i'm completely wrong.
Prime example... Diaz. I wouldn't have backed anyone on here to get the figures right for a proposed deal if you attempt to discuss agent fees and wages before we secured a deal for him. He doesn't seem one of those players with an agent looking for a huge cut or demanding astronomical wages.
To fully answer this would take quite a while. What I would say is the true cost of signing a player should always be fully understood, no? If Mbappe signed at Real Madrid instead of PSG was that truly a "free" signing? Is Haaland's cost comparable with with other £60m signings? For Haaland, how much do you bet if he's doing well we're going to hear non-stop next season the £60m that was paid and what a deal it was without mentioning the other £150m+ also being paid?
Wages across clubs and leagues are not standardized as well so to assume what Barca pays their £50m signing and what Arsenal pay their £50m signing are the same is clearly not true when you just look at their respective wage bills.
Diaz for instance, I wouldn't make any assumptions. LFC under FSG have had no problem paying Agent fees and our wage bill is top 5 in the world. Diaz isn't going to be on peanuts even if it may pale in comparison to what Haaland or Mbappe is getting.
All of this as you're noting is due to the lack of transparency aside from the transfer fee itself so that's what people go on. You can infer it by the books of the club the following year but it's never cut and dry, hopefully it starts to be reported more regularly though as it gives fans a better understanding of what something is or isn't truly costing.