Manchester United boss Jose Mourinho has voiced his concern about the way clubs are "spending £30m, £40m, £50m in such an easy way."
The 54-year-old has splashed the cash since replacing Louis van Gaal at Old Trafford in May 2016, highlighted by the £89m and £75m captures of Paul Pogba and Romelu Lukaku respectively.
But what Mourinho does not like is the excessive transfer fees that are currently being paid for players that do not fall into the world-class category.
"I always thought the problem is not what you pay for these kind of (top) players, I don't think the problem is what you pay for Pogba, I don't think the problem is going to pay crazy for Neymar," the Portuguese told several national newspapers.
"I think the problem is with the other group which is a big group because players like Pogba, there is one or two (big) transfers (like that) per transfer window. The other ones are where you have 100 transfers and for me that is the dangerous area of the market.
"Some clubs are paying or they don't buy because they don't accept the numbers that are now ruling the market, or to do it they have to go the same levels and for me that's what worries me a little bit because now we speak about £30m, £40m, £50m in such an easy way."
While the likes of United, Manchester City, Everton and Chelsea have all spent big money this summer, Tottenham have yet to dip into the market.
They lost Kyle Walker to City in a £50m deal but have so far managed to keep their other best players at the club, even thwarting Mourinho's reported pursuit of England international Eric Dier.
"Everybody speaks about the dimension of the investment at Man City, but there is another team that I feel the dimension of their investment is also phenomenal - Tottenham," Mourinho said.
"I think until now they spent zero pounds, right? For me the dimension of their investment is amazing. They keep everybody they want to keep. They keep Dele Alli, Harry Kane and Toby Alderweireld, they keep Eric Dier, they keep everyone they want to keep."
Mourinho is still on the hunt for two new signings and is confident executive vice-chairman Ed Woodward has the situation under control.
Only Lukaku and Victor Lindelof have arrived in a window that has seen United make slow progress on further targets.
Woodward joined up with United's American pre-season tour having stayed back to work on deals that the United manager is confident the executive vice-chairman has a grip on.
"I don't know," he said when asked if any progress had been made on transfers.
"Honestly, I don't know. Ed is in control. He did Lindelof and Lukaku, he knows that I would like two more players, but he also knows that I have balance.
"I understand the situation, I understand the market and if my club is not able to do two players and do just one, I will accept that as a consequence of the market now.
"Our relation is good and I just wait for good news - and he knows that for me good news is to have the players, or in this case maybe just the player as soon as possible because to work together with the team is really, really important.
"But I'm calm. I like my players, I like my squad, I trust them, so I'm calm and that's important."
Mourinho has, though, in recent months admitted there are certain players that he would have kept at United. He says he would never have sold Angel Di Maria, Danny Welbeck or Javier Hernandez, saying the latter was the kind of "killer" striker United would have loved last season.
Two years after Van Gaal allowed the Mexico international to leave for Bayer Leverkusen, he is back in the Premier League and could be lining up against United for West Ham on the opening day.
Asked if he was tempted to bring Hernandez back to the club, Mourinho said: "No, because he left the club a few years ago. I am not sure that it was his decision or the manager's decision.
"But he's a good player, he's a player that will always score goals, so he is a player I would always welcome in my squad because he doesn't need many minutes on the pitch to score a goal.
"But we moved in another direction and a younger player in Lukaku. We have (Marcus) Rashford that can be also a striker, he is originally a striker, so we didn't feel that need.
"But no doubt that for West Ham to get a player with his experience and his quality is very, very good."
