I sincerely think Buchnevich has a lot of talent, but I feel like Rangers fans overrate him a bit. The organization has selected a natural RW in the top 10 in each of the past two drafts, both significantly more naturally talented than Buch, and if they keep Strome in the fold, have a middle-six player who can play either C or RW (Strome is probably better as a winger at this point). Fast is a wild card, but if he is on the roster, he is always moved up/down the lineup depending on fit/injury.
Colorado has MacKinnon-Kadri -- rolls right off the tongue -- down the middle 1-2 for the next three seasons. Compher, who I like a lot, fits nicely as that third line C/LW who can move up the lineup if needed and just signed a great contract. Him and Kadri at their $ give the Avalanche a significant three-year window starting now. Newhook is going to be very good -- but obviously 2-3 years away -- and will probably be the contingency plan for Sakic once Kadri's contract starts approaching the end. Jost can either stay at C, challenge for that third-line spot and have Compher play the wing and ride it out, or make a more permanent position switch.
Even after signing Donskoi and trading for Burakovsky, I think the Avs could definitely utilize another potential 20-goal winger who fits their timetable (they're ready to start competing this year and Buch's goal-scoring would fit in nicely with that roster group). At best, the hope with Jost is he makes a significant leap and locks down that second-line LW spot next to Kadri with Donskoi/Burakovsky on the other side this season.
I think value wise, it's pretty even. I'm definitely in the minority, but I would add another non-significant asset to get the center. Kreider would likely be a one-and-done player, and I now highly doubt he gets a first-round pick in a trade until the deadline. Trading a player and trading for a player like Jost obviously carries significant risk from both sides, but he still has really good upside. Gorton made a similar move swapping Brassard for Zibanejad, but in this case obviously the age range makes each player enticing enough for both teams.