I'd surprised to see the club spend 20m+ on this guy now, it makes little sense.
Yes, he's a promising player but on the other hand he doesn't play for shitty Genoa. January is usually for fixing squad because of injuries or simply buy cheap kids (Rovella) or season wonders (Kulu).
In Juve's case it'd make more sense to get Papu - a proper game changer that can start some games or be used as impact sub. He's totally on Juve's level, he wouldn't need much time to adapt, unlike Scamacca.
Sure, if Scamacca makes a breakthrough, he'll cost much more. In Juve's case this is good IMO, it's better to buy a better product for a higher price, than spend quite a chunk of money simply for potential, which Pirlo won't be able to use anyway.