Kylian Mbappe's move from Paris Saint-Germain has been named the worst-value deal of the transfer window, while Mohamed Salah's switch to Liverpool is the best bargain.
The CIES Football Observatory has released analysis on the deals conducted in the last window, which found PSG got the worst value of transfers in Europe's top-five leagues in landing Mbappe from Monaco in an initial loan that they will make permanent for EUR180million.
Their algorithm, which "scientifically estimates fair transfer values" rated Mbappe, 18, to be worth EUR92.6m, meaning PSG will overpay by EUR87.4m in the deal, once add-ons have been taken into account.
Liverpool, meanwhile, landed the best bargain, according to the Observatory, with Salah bought from Roma for a cool EUR50m despite being valued at EUR69.4m.
Other teams guilty of overpaying were Barcelona and Manchester City. The analysis showed Ousmane Dembele, whose total cost could reach EUR147m, was added for a fee that was EUR51.2m higher than a fair value of EUR95.8m.
City, meanwhile, splashed out EUR57.5m on Benjamin Mendy, who was listed as a EUR28.5m talent.
Pep Guardiola's side were also on the wrong end of another deal. Of the sides to land the best bargains after Liverpool's move to add Salah, Sevilla's signing of Nolito from City for EUR10m - when he had been valued at EUR27.4m - came in second.
Chelsea's EUR39m move for Antonio Rudiger , who was rated as a EUR54.2m player, was third-most shrewd addition.
The CIES Football Observatory said: "As usual, a negative gap was measured between amounts paid and values estimated.
"On average, the former were 30 per cent lower than the latter. It is the biggest difference observed since the implementation of the transfer value algorithm. This finding reflects an acceleration of the inflation occurring in the transfer market."