Nobody is spending 100m per player, not even City. Our best signings have been cheaper signings. Our most expensive have tended to be flops.Don't you think everybody wants to sign the right player? What big spenders are doing is încreasing their chances of getting that right player through spending a bigger amount of money. A team spending an 100m/signing will EVENTUALLY have a better team than one spending 30m/signing.
There's no guarantees in football (see the list of expensive footballers that haven't been worth it that @Lilbaz posted)