Arsenal manager Arsene Wenger admits it is "scary" to see how much other teams are spending during the summer transfer window.
Chelsea spent £65.2million to secure the services of striker Michy Batshuayi and midfielder N'Golo Kante with Manchester United spending £56.3million to add Eric Bailly and Henrikh Mkhitaryan to Jose Mourinho's squad.
And the Red Devils are expected to spend at least £90million to sign French midfielder Paul Pogba.
The Gunners completed the transfer of three players so far this summer but are expected to add a defender and a striker before deadline day.
"[A top four finish?] It's never enough," Wenger told reporters.
"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. It's a big ask, because when you look at the Premier League, every club is hugely ambitious.
"You look at the cheques that everybody signs and it's quite scary. That's what the Premier League is about at the moment."