The Telegraph claim the Magpies have slapped a £150million price tag on their star striker to try and fend off January transfer interest.
This would smash the current Premier League record of £115m that Chelsea paid for Moises Caicedo.
This is the same figure that Newcastle quoted the Blues in the summer to ward off transfer interest.
Isak is the hottest striker in the top flight right now, scoring seven goals in his last five games.
Only Mohamed Salah [16], Erling Haaland [13], and Cole Palmer [12] have scored more than Isak's 11 so far this campaign.
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Newcastle are keen to keep hold of the striker amid strong interest from Premier League rivals.
Arsenal have been the club most heavily linked with the Sweden international, but are likely to balk at that price tag.
talkSPORT understands that Newcastle are under pressure to sell owing to profit and sustainability pressures [PSR].
We reported earlier this month that the club are braced for offers for Bruno Guimaraes amid Man City interest.
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Isak is another of their prized assets that could draw bids once the transfer window opens.
talkSPORT host Henry Winter told the Sunday Edition: "Where have they plucked the figure out? Where do you get £150m from? Three years left on his contract.
"£150m is a nice round figure, but there are also issues with PSR, they went through that with Elliot Anderson.
"If it is £150m, where does the negotiation start? Arsenal should be interested because they need a centre forward and their budget is sort of 80 million for a top striker. Where do you go with £150m?
"Basically I think Isak's not going to leave."
Newcastle are next in action on December 30 against Manchester United at Old Trafford.