Not sure if your issue is the fees or even just making a marquee signing out of Mbappe in the first place.
If the former, well, City have money, I'm not sure that's such a concern and would be unlikely to handcuff our other expenditures.
If the latter, wouldn't that extend to Gabriel Jesus or Leroy Sane too? Both came, both less tested and proven than Mbappe, both have exceeded most of our wildest expectations in their inaugural season. Could be the Pep factor, or not, but if the club are willing to sink a world record fee into this kid then it's not just because he has promise and nothing more.
When have Arsenal ever spent big? They can, but they just don't.
Dippers maybe?