I think it's really hard to tell just from spending (although it has provided a good guide in the past) as it's hard to quantify if (for example) a younger player or from a lower division steps up to be first XI material.
An example would be Liverpool, TAA and Robertson probably saved them £100m. Kane similar for us. Saliba could be great for the goons etc.
Personally I think the manager is more important these days than ever. And decent ones are thin on the ground. They are the ones to make sense of it all, improve players of all levels. Plenty of clubs can pour money into a hole...United Villa Everton...and our own Conte has stated, referring to us, you can't make mistakes in the transfer market.
We obviously have a good one, we just need to keep giving him what he asks for, it's really then on him to deliver.
Fwiw...Im not convinced by Arteta or Ten Haag....so the money will only help so much.