The Manchester clubs' combined 322 million pound ($417.41 million) expenditure made up over 40 per cent of the league's total 794 million pound summer spending since May.
United paid a world record fee of 89 million pounds to bring Pogba back to Old Trafford from Juventus on Tuesday, while City signed England defender Stones from Everton for 47.5 million pounds later that day.
The Manchester rivals have also spent big on the likes of Ilkay Gundogan, Nolito, Leroy Sane (all City), Henrikh Mkhitaryan and Eric Bailly (both United), and both clubs have a summer net transfer spend of over 40 per cent of their annual turnover.
The spending power of the Manchester two underpins the dominance of the 'Big Six', with Arsenal, Chelsea, Liverpool, Tottenham Hotspur, City and United spending 529 million pounds since May, twice as much as the rest of the league combined, according to Spreadex's figures.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
The outlay of the Big Six dwarves the league's average spend per club of 23 million pounds, while only four sides have turned a profit to date this summer.
Southampton, who sold Sadio Mane to Liverpool for 34 million pounds, Graziano Pelle to Shandong Luneng for 13 million pounds and Victor Wanyama to Spurs for 11 million pounds, have made the greatest profit of the division to date, with 40 million pounds.
Everton, Swansea City and Hull City are the other teams to have made a net transfer profit so far this summer.
(Reporting by Ed Dove, editing by Susanna Twidale)
