Ronaldo returned to Old Trafford, 12 years after leaving for Real Madrid, and is set to make his second debut for the club against Newcastle United on Saturday.
CIES Football Observatory have put together a list of the most valuable football clubs in the world right now, with Pep Guardiola's side ranked first with a squad value of £924.5m.
United sit second with a value of £878.5m, while Paris Saint-Germain, who added the likes of Lionel Messi, Sergio Ramos, Gini Wijnaldum, Achraf Hakimi, and Gianluigi Donnarumma are third with a squad value of £806.4m.
Top 10 most valuable football clubs in the world right now:
10. Tottenham Hotspur (£473.2m)
9. Barcelona (£496.4m)
8. Arsenal (£541m)
7. Juventus (£564.2m)
6. Liverpool (£577.1m)
5. Chelsea (£669.8m)
4. Real Madrid (£675.9m)
3. Paris Saint-Germain (£806.4m)
2. Manchester United (£878.5m)
1. Manchester City (£924.5m)
PSG president Nasser Al-Khelaifi discussed Financial Fair Play at Messi's unveiling last month and insisted his side were within the limits. He said: "Regarding the financial aspect, I will make it clear - we know the rules of FFP and we will always follow the regulations.
"Before we do anything, we check with commercial, financial and legal people. We have the capacity. If we sign Leo, it's because we can, otherwise we would not have done it. "What Leo brings to the club is huge, which you can see just outside (the stadium, where thousands of fans had gathered). He is a big asset. I hope Leo will not ask for a raise of salary, but what we have is fantastic."