Thing is with these sort of teams that they have a lot of fans, but they aren't really football followers or understand things to any degree, they just like football and a team, nothing else really exists to them. It's just a bubble and everyone wants to play for their super team. I'd say this probably accounts for 70% of fans, maybe more.
You only have to look at the 'YNWA' or 'Welcome to Liverpool' comments that flood every Youtube video or transfer story, and this is a team who has been off the radar for years. They just don't understand, it's pure ignorance. What can you do?
Irony really. Even when you step away from the ones linked to a club by geography or culture. Just the other day, we finished a game of footie, and were talking tactics at the end of our game, when a kid spurted out, almost non-chalantly referring to the Chelsea-Utd game as the perfect tactical plan when soaking up pressure etc. almost like that is pretty much the frame of reference for everyone who breathes, and like it was a given that all of us were fans of either of those two clubs. Like there was no other league in the world, no other teams in the world.
Most kids come in their favored club jerseys. So there's an overwhelming bunch of Utd, Chelsea and Arsenal kits. Off late, I've been noticing the odd Bayern jersey too (glory hunters ahoy!?) and the one that really made me sit up and take notice was an inter jersey. Needless to say the kid looked like a daft punk. While my brother and me show up in our Juve jerseys.

Another interesting thing I noticed, was a bunch of people just liked the look of the Juve jersey this season (away) and wanted to buy for that reason. It's an interesting trend to notice, when a team is devising marketing strategy. Somewhere though, I can't even blame the modern generation of kids. The EPL is packaged and marketed way better than the other leagues followed by the La Liga. Adding to the hype and educational aspects that most kids/young fans coming into the game would pick up on quicker than other leagues.
United fans think they have a chance because they think Vidal is on low wages, not realizing that in Italy teams present their players salary after tax unlike what they do in England. The money that Vidal gets from Juve would make him a top 10 earner in England.
And I'm pretty sure that we could pay Vidal over £200 000 pounds a week(top 5 in England) if push comes to shove. Conte will kill people if Vidal ends up leaving. That is his main guy.
Utd fans or the type that Jay described anyway, don't have the intelligence to factor in something like wages at all, or go to the extent to understand what you've said above. Theyd think they could get Vidal on a very superficial level - in the sense at they are Utd, and Utd is the be all and end all of football. Juve don't stand a chance because they're up against Utd and the Epl. - the only legit league in football. That's all there is to it. No calculations of whether they'll be in the CL next season. No calculations that they would need to break the bank. And no calculations that Juventus are histiorically on par with Utd if not bigger.