I don't know how true this is... But if it is then it would be the reasonable thing to do for Sporting. Because there is no way they are selling him for a price like 85 million pounds (~100 million euros).
His market value is 75 million euros according to Transfermarkt. They should be more reasonable with the price. He is a great striker but expecting 100 million for him is too exaggerated.
Sporting seem to realise that the (previous) asking price is quite high, therefore they have taken the initiative to lower the value and I think this is more realistic. Viktor Gyokeres had a good season with Sporting and he performed quite impressively there, but there is no guarantee that he will be able to continue his good form when he moves to a new team in a more competitive league. Therefore, 100 million is too much and he might end up with the same fate as Darwin Nunez.