It's a balancing act, not sure you'll be happy with a 20M kid who's 2 or 3 years away from performing, while Mbappe is more expensive, he could offer something straight away.
I don't think we're breaking any banks though, for any player, we're Arsenal, the culture has always been conservative.
Probably not over Mbappe, but I'd rather we took a couple of risks on guys like Gabriel Jesus and Barbosa than the likes of Lacazette.