Warren Buffet once said he prefer investing his money in a pesimistic market cause he like the prices pessimism breeds. Mbappe this summer will be quite the opposite with him and Monaco being "in the zone".
While being efficient and converting chances is a good sign for a striker, its unlikely that he will keep it up for a longer period. Right now he has a conversion rate close to 30 %. In ten years it will be around twenty percent (IF he lives up to the hype). Since 2009 Messi is at 21 %, Lewandowski 18-20 % etc.
The convertion rate, combined with Monaco creating lots of chances, helps build a huge hype. Monaco should consider selling him this summer.