A lot if you find the right team. He’s playoff struggles will scare some teams. I think you need to find a team that is good and he makes them great without being the best player. You need an elite prospect or high end nhl player with room to grow depending on if you are rebuilding or retooling. Anything less than that, good luck

My ask right now would be what Colorado got for Duchene.

My guess: Another useful winger, A good prospect, One first round pick, One later conditional pick

Using teams from East as rough/quick examples....

BOS: Debrusk, Studnicka, picks
BUF: Skinner, Cozens, picks
NYI: Bailey, Wahlstrom, picks
NYR: Kreider, Kravtsov, picks
NJD: Gusev, Mercer, picks
PHI: JvR, Zamula, picks
PIT: Zucker, Poulin, picks
WAS: Vrana, Leason, picks

Depends largely if he agrees to sign atleast 5 year contract with reasonable salary. Now when he got 1 year left, it hurts the value.
Something like Nylander + small sweeteners Im guessing.

1st, 2nd, b+ prospect. or just a hockey trade for another player that needs a change of scenery.

Everyone here has no idea what his value is, but I think it has to be really really high

Higher than what people think on this site, lower than what Flames fans think on this site. I saw someone say that Gaudreau isn't even a starter in a Nylander trade which is psychotic and wrong but then I have seen Flames fans think he is a headliner piece in an Eichel trade which is also wrong.
I think a good comparison trade is the Pacioretty trade if Calgary is going into a rebuild, you need to find a team like Vegas that was going absolutely all in that year similar to a Colorado, possibly Montreal or if Boston wanted to put it all together for one more run.

For Colorado I think the ask would be something along the lines of: Bowen Byram, Donskoi and a 2nd
Montreal could amost replicate the Pacioretty trade: Tatar, Kotkaniemi and a 1st round pick
For Boston I think it would be something like: John Beecher, Debrusk and a pick

Colorado Montreal and Boston fans would likely feel uncomfortable giving that up and Flames fans will feel like they're not getting a good return