Therein lies the problem, though. Getting a world class player does not guarantee winning things. Ask PSG who have been in as many PL finals as us.
You may be better off getting two very solid players for the same money, that will actually make the team better than the one world class one.
The opportunity cost is the ability to strengthen meaningfully in several positions (like you say) and also perhaps the added pressure to selling players.
You also don’t spread risk when you buy one big player instead of multiple mid players.
Excluding Bellingham… How many of these top 10 most expensive players were worth the outlay:
1. Neymar to PSG - £198m
2. Mbappe to PSG - £163m
3. Coutinho to Barcelona - £105m
4. Joao Felix to Atletico Madrid - £113m
5. Enzo Fernandez to Chelsea - £107m
6. Griezmann to Barcelona - £107m
7. Grealish to City - £100m
8. Lukaku to Chelsea - 97.5m
9. Dembele to Barca and Pogba to Man Utd - £89m
Coutinho, Felix, Griezmann, Lukaku, Dembele and Pogba look like obvious NOs.
Neymar, Mbappé and Enzo MAYBEs
Grealish YES
Expensive transfers are rarely clear successes. Does rice deserve to be joint 7th most expensive player in history?
I don’t think so.