There are a few cases of high-end wingers being traded that we can look to. I'm going to breakdown a few, and you'll see that multiple high-end seasons as well as seasons with high point totals, NOT point paces, matters in a potential return. Let's look at a few cases and evaluate the player based on age, pedigree(number of seasons with 1st line+ production), and statistics. These player were at least in somewhat similar contract situations. This obviously isn't a fool-proof system for interpreting Fiala's value, but it should give us an idea of the range of outcomes.
*Let's define 1st line production. There are 90 first line spots available in the league. Some teams have 6 first line caliber players, others have none. The 90th forward in ppg this season (min. 30 games) is Jeff Skinner with a .779ppg, or a 64 point pace. This year is far higher than normal for scoring, so I'm going to use the middle ground between now and 2015 as some of these players were traded a while ago. In 2015, the 90th ranked forward in ppg (min 30 games) was TJ Oshie with a .638 ppg, or a 52 point pace. A more accurate way to do this would be to adjust each player's stats relative to the season the produced those stats in, but that seems like a lot of work. I'm going to use the middle of 64 points and 52 points as the cutoff for a 1st line forward (58points / .707ppg)
Buchnevich:
Age when traded: 26
# of seasons w/ 1st line production: 1
points per game last 3 seasons: .709
Career High points: 48
return: Blais + 2nd
Paccioretty:
Age when traded: 28
# of seasons w/ 1st line produciton: 6
points per game last 3 seasons: .74
Career High points: 67 (39 goals)
return: Suzuki, Tatar, 2nd
Reinhart:
Age when traded: 25
# of seasons w/ 1st line produciton: 3
points per game last 3 seasons: .75
Career High points: 65
return: 1st + Levi
Fiala:
Age when traded: 25
# of seasons w/ 1st line produciton: 3
points per game last 3 seasons: .9
Career High points: 77 (5 games left in season)
return: you tell me
I think Fiala should return more than Reinhart. Buchnevich wasn't really close to Fiala's profile at the point he was traded (a trade that many thought was bad immediatly no less) so he's not a comparable for me. Fiala is a statistically better player than Paccioretty, but pedigree talks and scoring is up this year compared to Patches prime. Fiala's age is favorable, though. I would bet that Fiala's return will fall somewhere in between the Reinhart return and the Paccioretty return.