Napoli president Aurelio De Laurentiis admits the club rejected an offer of 55million euros for Edinson Cavani this year, revealing the striker's value is now set at 63million euros.
The Uruguayan has been linked with potential moves to Barclays Premier League sides Chelsea and Manchester City, as well as Primera Division outfits Real Madrid and Barcelona, after hitting 13 goals in Serie A this season.
Cavani scored 49 league goals in the preceding two seasons since joining Napoli from Palermo in 2010, and De Laurentiis confessed the striker's impressive form invited a significant bid from an unnamed club this summer.
He told Gazzetta.it: "Last summer I was offered 55million euros (approximately £45million) to release him but I didn't sell.
"Then in September we fixed his release clause. All things considered, buying him would cost 63million euros (approximately £52million)."
Napoli are 10 points shy of league leaders and reigning champions Juventus having been issued with a two-point deduction for their "objective responsibility" for a former player's attempt to fix a match in 2010.
Club captain Paolo Cannavaro and fellow defender Gianluca Grava have also received six-month bans for failing to report goalkeeper Matteo Gianello's approach to fix Napoli's game at Sampdoria two years ago.
De Laurentiis added: "We are going through a bad time because of Cannavaro and Grava's bans, and because of the points deduction.
"But I have decided to stay in football and so I will obey the rules, even if certain punishments do serious damage to your finances, football and public image."