Sancho has scored 17 goals and made 19 assists in 35 games for Dortmund this season.
United are interested in signing the 20-year-old this summer but face a battle for his signature from other top Premier League sides as well as Europe's elite, with Barcelona and Bayern Munich both keen.
But considering the potential of Sancho, the prices have been evaluated as fair in the current market.
Some absolutely pointless Jadon Sancho to Manchester United speculation, then?
Grealish would be an excellent signing if United could pull it off but his arrival would cast further doubt over the future of Paul Pogba with the Frenchman being strongly linked with a move away from Old Trafford this summer.
Recent reports, though, have seen a clear frontrunner emerge in the Sancho sweepstakes.
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Sancho is said to favour a return to his home country over a move to Spain, with the Red Devils an enticing option.
"Jadon Sancho would probably be number one".
United, for their part, meanwhile, are viewed as in an ideal position to "exploit" the uncertain nature of the upcoming transfer window.
Speaking on Instagram Live this morning, Juan Mata was drawn on the speculation linking the Red Devils with the gifted attacker. We all know that he's a great player.
'We all know he's a great player, he's having a fantastic season at Borussia.
Reus told German magazine Sport Bild: "I would advise him to stay at BVB for another year, maybe two".