Like I said... the difference in opinion between those that have watched him regularly vs those boiling him down to xG overperformance. If he was purely an xG overperformer than United would have got away with paying a lot less.
He underperformed his xG by 5.5 in his first season in the Prem, whilst the season before last he was on for ~15 non-penalty goals before he got injured and missed almost half the season. His impact at both ends of the pitch makes him a complete player - only second to Salah, and miles ahead of third, for progressive passes received, whilst led the division for tackles in the defensive third for any forward. Add twenty goals from the wing into that and he's an elite performer at this level.
Trust me, United have got a bargain.
I dont really care what the costs involved are - thats up to the club to decide if they're happy with the price. I'm just sad I won't get to see him play for Brentford anymore... it's been a great six year spell. Oh well, just bought my ticket for our opener away at Forest, so that's something to look forward to!