If I had to make a guess, I would say the following -
1. PSG's bid is enough for Monaco.
2. Mbappe is fine with PSG (and City and Madrid).
3. Monaco are going to hold onto PSG's bid for a while to see if City or Madrid match it or come close to it.
4. If that happens, they'll happily sell Mbappe to City/Madrid.
5. If that doesn't happen, they'll bite the belt and sell him to PSG for what looks like a crazy amount.
Again, all guesswork.