Man City have a transfer tax that Manchester United are years away from

There was some grumbling from Old Trafford recently at what they saw as a 'United Tax' - selling clubs deciding to charge more when they saw how deep the pockets of the buying club are.

The transfer market is a curious thing given how much subjectivity there is in valuing players amid different circumstances around supply and demand. To take two recent examples, United could drive the price for Mason Mount down because Chelsea were under pressure to sell, but Ajax could charge more for Antony last year because they had already sold players and there was limited time left in the market to sign a replacement.

Despite the unique pressures around deals, there is a framework by which clubs buy and sell. Each player can only ever be worth what the buyers are willing to pay and over time those decisions dictate how prices go up and down across a market.

Manchester City routinely overpaid for players in the early years after their takeover in an effort to fast-track their way to the top of English and European football. However, for all the Robinhos and the Jos they also had major success by putting together financial packages that may have seemed pricey but turned out to be incredible value: Yaya Toure (£24m), David Silva (£24m), and Sergio Aguero (£38m) were the first and among the most high-profile of these deals that gave remarkable bang for City buck.

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This has been honed and amplified in the Txiki Begiristain era under Pep Guardiola, starting with the very first signing of Ilkay Gundogan for £20m. Kevin De Bruyne (£54m), Bernardo Silva (£43m), Ederson (£34.9m), John Stones (£47.5m) and Kyle Walker (£50m) were among the stars bought between