Aurelio De Laurentiis says interested parties must pay the buyout clause if they wish to sign the striker but conceded he is open to part-exchange deals if they represent value.
The Uruguay international is also a reported target for Chelsea after notching 102 goals in 124 matches for his club in all competitions over three seasons, but a player-plus-cash deal involving Edin Dzeko has stalled. De Laurentiis has always maintained that Cavani will only be sold if his 63 million euro buyout clause is met.
"City said that they can't pay 63 million euros for Cavani," De Laurentiis told reporters. "They can only afford Cavani if they sell first."
"I could accept a part-exchange deal if the players proposed are attached with a figure that represents the actual value of the player.
"[Edin] Dzeko for example, is no longer what he once was, he was not a starter last season. He did not perform how he did in the Bundesliga [with Wolfsburg]. This is assuming that Dzeko wants to join Napoli, of course."
De Laurentiis backtracked from his previous statement that Chelsea was interested in Cavani by claiming the Europa League winner is yet to make its interest concrete.
"Chelsea never made contact with me. I have always heard rumors indirectly," De Laurentiis said.
Cavani recently described a possible move to Real Madrid as a 'dream', but De Laurentiis says the striker's words were taken out of context, though admitted a move to Santiago Bernabeu would likely be hard to turn down.
"With Edinson nothing has changed," De Laurentiis said. "Headlines I've read in the papers did not represent his words exactly. He could never deny the importance of a club like Real Madrid's, but don't forget that he made his name at Napoli.
"If a club like Anzhi inquire about him, maybe he says no, but other clubs like Bayern, Barcelona or Real Madrid could persuade him to leave.
"He knows that he has a contract and an obligation to us, and there is a buyout clause. Cavani knows that at Napoli is he is the most important player. I do not know whether, at Real Madrid or in other teams, he will be as important.
"[Cavani] will decide what to do and we will support him."