Manchester City boss Pep Guardiola and Liverpool manager Jurgen Klopp say they are bewildered by Chelsea's huge spending spree during the January transfer window.
Chelsea signed eight new players last month, taking their total outlay since the end of last season to more than £500 million ($605 million).
The Blues paid a British record of nearly £107 million to land Argentine World Cup winner Enzo Fernandez from Benfica on Tuesday's transfer deadline day.
In contrast, City spent just £8 million on Argentine midfielder Maximo Perrone during the January window, while Liverpool brought in Netherlands forward Cody Gakpo from PSV Eindhoven for a fee of 40-50 million euros.
Chelsea's spending since the Todd Boehly consortium's takeover at Stamford Bridge last year has prompted questions over how the club will meet Financial Fair Play requirements.
And Guardiola suggested City, given their past issues with FFP, would have faced considerable criticism and scrutiny had they matched Chelsea's level of investment in new signings.
"I know what would happen. It's none of my business but it's a surprise because it's not a 'state' club," Guardiola, whose club is owned by the Abu Dhabi United Group, said on Friday.
"What I'm concerned about is we won 11 trophies in the last five years being the fifth or sixth team in net spend in the Premier League. That is what really counts to us.
"Not just in the Premier League, but Europe, you have to spend. Now the market is 'wow'.
"What Chelsea do is not my business, I never involve opinions in other clubs because there are regulations, rules, that we have to do.
"But we were accused. I don't forget, eight or nine teams in the Premier League sent a letter to the Premier League for us to be banned. That happened to us."
- Klopp stunned -
Klopp was also stunned by the level of Chelsea's spending on improving Graham Potter's team, who are currently a lowly 10th in the Premier League, one place below struggling Liverpool.
"I say nothing without my lawyer -- that's a joke," Klopp said on Friday. "I don't understand this part of the business. What you can do, what you cannot do. However, it's a big number in the last two windows.
"The players they brought in, I didn't think once 'Why did they do that?' They are all really good players, so from that point of view congratulations when you can do it, and obviously they do it.
"I don't understand how it's possible, but it's not for me to explain how it works. Hopefully you all know exactly how it works, and then it's fine."
Asked if he expected an instant improvement from Chelsea after such a huge spree, Klopp added: "Yeah, Graham knows that.
"I'm not sure (co-owner) Todd Boehly is too much interested in that, but that will happen at one point as well that they will play well together.
"With the quality they have, that's hard to avoid. How quickly it will go, I don't know."