If an incredible offer came in then we would sell, nobody including Vidal is worth those types of money. But then again, every damn player not named Messi is available for an absurd transfer fee. That doesn't mean United are close to signing him.
And IF, and I mean IF United came in with a monster bid I'm pretty sure we'd give PSG a call as well and I'm pretty sure those guys would offer an even higher bid. And if the choice was Paris or Manchester, I'm pretty sure he'll be off to Paris.
Sure. I guess it depends what you define as an incredible offer. The highest amount I've seen reported that Juve want is 60m euros. The lowest I've seen reported in 32m pounds which is 40m euros. I guess the clubs will haggle for something in between.
Last summer, when Chelsea wanted Rooney, United stated clearly that he wasn't for sale at any price. Juve could have done that publicly already, but they haven't yet. That just encourages rumours like these.
The other rumour is that Vidal is especially keen to come to Manchester United, and not somewhere like Real Madrid. Obviously, just a rumour that may be rubbish. I have no idea how attractive PSG may be to him, and of course they could offer more money but they've already splashed 50m on David Luiz and have some FFP restrictions put on them (which they may decide to ignore completely).
The other thing helping English teams is that the pounds to euros conversion is very healthy right now. That may influence the market this summer.