We did that last summer, and look how that turned out. If the information below is correct, I'd say going to £100k would be fair, or walk away from the deal. Earning 5x your current wage should be enough considering his desire to join an EPL side instead of PSG.
If this was someone like Leao or Osimhen, I'd be more incline to agree with your thinking.
Edit: I'm going off the information here - Manuel Ugarte latest: Chelsea & PSG’s transfer offers, wage proposals, decision date - Absolute Chelsea
He's currently earning £25kpw, and we're offering him £143kpw~ (there's probably bonuses on top of that). Comparing us with the stupidity that happens in Paris is a non-starter (they are supposedly offering £358kpw).