Arsenal boss Arsene Wenger says "it's quite scary" to look at the money being spent to strengthen his Premier League rivals ahead of the new season.
Wenger spent £30 million on Granit Xhaka in May, but has yet to make another major signing, while the likes of Manchester United and Chelsea have both brought in several expensive reinforcements.
Manchester City are also closing in on a big-money deal for John Stones that could reach as much as £50 million, while United have agreed a record-breaking fee of €120m to buy Paul Pogba from Juventus, sources have told ESPN FC.
Wenger is still searching for a striker and a forward as the Gunners try to improve on their second-place finish with a first Premier League title since 2004. But the Frenchman has acknowledged that the money being spent by other clubs will make things a lot more difficult in the upcoming campaign.
"It's a big ask, because when you look at the Premier League, every club is hugely ambitious," Wenger said after Arsenal beat the MLS All-Stars 2-1 in San Jose, California.
"You look at the cheques that everybody signs and it's quite scary. That's what the Premier League is about at the moment."
Wenger is entering the final year of his contract and is under huge pressure to deliver a big title. When asked if another top-four finish in the league -- which he has delivered in all 20 of his previous seasons -- would be enough this time, the Arsenal boss said: "It's never enough. I personally believe that no matter what you do, it's never enough.
"You have to give absolutely everything to take the best out of the team. I believe that we know what we have to do, because we were second last year, we had 18 teams behind us."
The Gunners will have to make do without Per Mertesacker for several months after the centre-back sustained a serious knee injury and Wenger reiterated in an interview with ESPN that he still wants an offensive and a defensive signing before the end of the summer transfer window.
"We were a bit short on goals scored [last season], so we will try certainly to strengthen a little bit in that department," Wenger said. "Defensively we need to bring some more experience into our squad. I think in the middle of the park we have enough players."
Meanwhile Arsenal's rivals continue to splash the cash.