Value is relative to team needs - its not black and white. In a vacuum, Barkov is absolutely worth more. But to the Flyers? We don't 'need' Barkov like we need Provorov. Barkov's value to us is diminished by already having a superior center to him on our roster.
Provorov's value to the Flyers organization is because he projects as a bonafide 1D, which we havent had since Pronger. It doesnt matter if you offer us a great package for him. Our biggest need is 1D, and unless we are getting one for him (circular logic) it doesn't make the team better by moving him.