This is really really silly:
So if Man Utd buy Zinchenko from City for 50m and City buy him back for 50m.
Then next season the same thing happens:
Man Utd and City have both invested 100m into their squad and improved their squad with 100m of purchases?
It's ridiculous notion.
What the hell are you on about?
If Liverpool sell Coutinho for £140M and buy VVD for £75M and Alisson for £70M, net spend £5M, but they have still brought £145M of players. What are the two new players worth, £5M? No, £145M!
wtf is so difficult to understand?
Generally if you sell a player, because you have an offer you can't refuse and spend all the money on a either a replacement or to strengthen other areas, you have still spent the money.
You lot seem to think a team sells a £100M player and buys 100 £1M players to replace them, it doesn't work like that. Obviously Spurs bucked the trend by selling Bale and buying £100M worth of crap.