Take a look at the top scorers in the Premier League, and ask yourself how much they are worth.
Aguero, Kane, Lukaku, Zlatan, Costa. Put £50 million on the table and you’d be laughed at.
Do the same for La Liga; Griezmann, Ronaldo, Messi, and add another £50 million before you can even get yourself a discussion about a move.
No one would put Jermain Defoe in that class, particularly not at 34.
His true value probably lies at around £25, £30 million. That may seem steep for a player at his age but he is on a long-term contract, has no history of injury problems and can still get through a sequence of games in a short period without a rest.
His goalscoring record may well be padded out by penalties this season but it still stands up with the best over a long period of time.
Yet the crucial point here is not even a bid that reflects his actual value should tempt Sunderland to sell.
Take Defoe’s goals out of Sunderland’s tally and they are in danger of a Derby-esque record season.
Victor Anichebe and Fabio Borini would be less effective without him, defenders less pre-occupied with the poacher’s movement and presence alongside and in behind them.
Add, too, the emotional toll of losing Defoe. To the supporters it would quite understandably look like the raising of the white flag above the Stadium of Light, a sign that the club no longer have serious designs on retaining their Premier League status. Morale would plummet.
So there is only one circumstance in which Sunderland can even consider selling Defoe: If they can guaranteeing replacing his goals.
There are a few candidates across Europe who could do that, and would be available around the £30 million mark. Alexandre Lacazette at Lyon, Carlos Bacca at AC Milan.
Yet Sunderland would have little to no hope of attracting them in their current plight, even if they offered double currently what Defoe currently earns in wages. It’s no secret they have no money to do that.
The situation could change if Defoe decides the lure of home is too great, though he may question how valuable the Hammers deem him to be if £6 million is their price.
And the cold hard reality of cash in the bank may yet tempt to Sunderland. Common sense says they simply have to stand firm.