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The Turkish forward has been in fine form over the last 18 months, which has in turn meant he has become a transfer target for a host of English clubs.
Newcastle, Everton and Crystal Palace are said to be three Premier League clubs interested in signing Tosun.
While European heavyweights Juventus and Borussia Dortmund have also reportedly joined the race for his signature.
But all parties have been dealt a huge blow this week, with Besiktas vice-president Deniz Atalay sticking a whopping €100m (£88m) price tag on the 26-year-old.
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“He is starting to reap the fruits from the seeds we sewed”
Deniz Atalay
“If you ask me Cenk is worth €100 million, he has a very bright future,” Atalay said, according to Turkish Football.
“He is starting to reap the fruits from the seeds we sewed.”
Newcastle and Crystal Palace will be disappointed after missing out on the attacker in the summer.
The Eagles were close to securing a £22m move for Tosun before negotiations broke down on deadline day.
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But that figure is now unlikely to tempt Besiktas to part ways with their prized asset, who is enjoying a fantastic season at the Super Lig outfit.
Tosun has 11 goals and two assists in 19 games for the Black Eagles this season.
The former Frankfurt man has been performing particularly well on the biggest stage this term, netting four goals and grabbing two assists in five Champions League games so far.
Besiktas have already booked their place in the knockout stages of the competition.