The Juventus general manager believes the 26-year-old Chilean midfielder is just as valuable as Real Madrid's new world-record signing.
The Welsh winger made a world-record 100 million euro move to the Bernabeu this summer from Tottenham after starring in the Premier League last term.
However, Marotta is certain that the midfielder is worth just as much as the 24-year-old after starring for the Italian champion for the last two seasons.
"If Bale is worth 100 million euros, then the same goes for Vidal," he told Mediaset. "Real Madrid expressed an interest this year, but selling him is out of the question so the interest ended there."
Marotta also voiced his praise French midfielder Paul Pogba, who has established himself as an integral part of Antonio Conte's side since moving from Manchester United a year ago.
"We can say the same about Pogba [as Vidal]," Marotta added. "He's a solid element of the team and we've turned down all the offers we've received for him.
"He's exploded in an almost unexpected way, so compliments to the lad but also to (Antonio) Conte who has managed to get the best out of him. If he confirms his status at the highest of levels, as we obviously hope he will, then this should be recognized with an increased salary."