United have targeted Sancho all summer though are believed to have been put off the £108m fee that the Bundesliga outfit want.
United boss Ole Gunnar Solskjaer has made just one signing so far this summer with Donny van de Beek the only arrival at Old Trafford.
Though, with a sense that the Red Devils are getting desperate to improve following defeat to Crystal Palace, Dharmesh Sheth has explained that Dortmund could raise Sancho’s asking price.
Sheth said on Sky Sports News: "The danger for United now is the following.
"Such has been their focus or concentrating on one target, namely Jadon Sancho, they've seen their rivals, the likes of Liverpool, Chelsea, Tottenham, Arsenal, Manchester City go out and do their business.
"As a result, with just 13 days left in this transfer window, any player that Manchester United go for, the selling club will think: 'Well hold on, we can smell desperation here from Manchester United because they've left it this late, if they're going for one of our players, perhaps we can increase the price'.
"There's already what's called a Manchester United tax when it comes to transfers isn't there.
"If Manchester United are interested in a player, the price will go up. That will only be reinforced the later we go in this window."
United legend Gary Neville has said that his former club do look desperate in the transfer window.
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He said: "It's just a thing with United that every time they go for a player in the last four, five, six years it feels they are a little bit desperate.
"They think they can hang on but they always pay it (the asking fee) in the end.
"That's sometimes where I think you can take control, give a hard deadline and say 'we're moving away from this deal’.”