The Portuguese spent wisely during the most recent window by bringing in Romelu Lukaku, Nemanja Matic and Victor Lindelof, while also landing free agent Zlatan Ibrahimovic for a second stint at Old Trafford.
Mourinho is happy to have finalised each of his big-money transfers, totalling just short of £170m with add-ons, before the likes of Neymar and Ousmane Dembele moved for astronomical nine-figure fees.
"I think we were very clever," Mourinho told The Times. "We thought that something could happen that could change the market forever. Normally the last part of the market is less expensive, but this season, after Neymar, everything changed - and changed for the worse in terms of prices.
"I think Lukaku on August 31 would have been £150m. Matic would have been £60m or £70m. Neymar changed everything. If the biggest transfer in history had still been Paul Pogba, I think Philippe Coutinho would now be in Barcelona at £101m. People look at the £200m figure now. Now the players of £20m became £40m, the players of £40m became £60m and everything changed.
"Lukaku and Matic, now, would have cost us £200m in total. But because we did it in the first part of the summer, it was much less. I think we did well in financial terms and well in preparation terms, getting them before the season started. That is not crucial but it is important."
Mourinho signed Pogba for a then-record sum of £89m in 2016, but Dembele and Neymar each overtook him this summer.