Very few players want to be in Buffalo, if they did they would not be where they are.
I know some Ranger fans want to think they'll get him cheap, yet Buffalo would be far better off keeping Eichel and trying to build around him. He can't just choose to go anywhere else, or not extend, or only extend until his RFA years are over. He can complain and that's about it.
What are their other choices? To take some prospects who were drafted outside of the top couple picks, like they have amounted to much of anything on Buffalo in the past? Or picks that too would be outside of the top couple picks? Maybe they develop another Reinhart or Ristolainen at best?
Or wait until some other team ends up with a player near his caliber that does not want to be wherever he is, where Eichel, nor that player also does not want to be or go to?
Not trying to say Buffalo will not do something dumb, more so saying if they do trade Eichel is will turn out to be not much in 5 years for them.
As far as the Rangers trading for Eichel that would also end up disappointing, they'd eventually become some form of the Buffalo roster due to both the return going back for him, and his incoming cap hit. Eichel without Zbad, Buch, the return for Eichel, and take your pick of whatever good young cap casualty while they are still married to Trouba, Kreider over the next 5 years ends up poorly.