And Moncada was best in baseball prior to 2016 season, and still top 2-5 at the end.
Point is, they had a luxury of having 2 top top prospects, and could therefore pick which one they didn't want to give up, and still trade a better prospect than 28 other teams.
If they didnt have Moncada as another top 2-5 prospect aside from Benintendi, they would have traded Benintendi, or they wouldn't have gotten Sale.
No prospect is untouchable when a top talent MLB player or pitcher is being traded for.
But I think you clarified your point as I was typing this, you feel Conforto is past the point of prospect status so he wouldn't be what the Mets want to part with, since he's proven to be more of a sure thing already. I can buy that as a valid stance despite that I disagree with it