Chelsea are also planning to intervene and make an offer for Mbappe according to some sources. Technically Al-Hilal have a way bigger potential offer for Mbappe. They are planning to offer 200 million euros for his transfer fee and 400 million euros per year for his contract also. This is like a dream offer for any player for sure.
However I don't expect Mbappe to accept any offer outside Europe at least for now. Therefore Chelsea should be comfortable about that. They had better meet PSG and Mbappe's demands both firstly. After that they will most probably have to fight against Real Madrid. I don't think Mbappe would prefer Chelsea to Real Madrid.
I'm pretty sure the news regarding Chelsea for Mbappe is just gossip. because, besides Mbappe's expensive price. it is very likely that Chelsea will be subject to FFP sanctions later. however, even if the rumors are true, I believe it is likely that Mbappe will turn down an offer from the Blues. simple answer, Chelsea did not enter the Champions League. Also, it looks like Mbappe is not interested in a Premier League club.
As for Al Hilal, whatever their offer is for Mbappe. I'm quite sure, the player will not be willing to play in the Saudi League. the reason is, it's not just money that is Mbappe's priority. but he wants to be a great star, like the megastar he idolizes, namely Ronaldo. I mean, Mbappe wants to win many trophies from prestigious events including the Champions League trophy. Besides that, he wants to get many awards for his achievements. therefore, I dare say that Mbappe would not be interested in leaving for a club other than Real Madrid. with Madrid, Mbappe has a way to smooth out what he aspires to in his football career.
if, Chelsea is willing to pour out the funds according to what PSG wants. sadly, the final decision rests with Mbappe. if the star refuses, that means, PSG can't let him go. Well, as I said before, the Mbappe transfer saga will be quite tough.