Not sure if that's fair. Carter was traded midseason and put up 0.64 PPG with the Blue Jackets, who went on to be literally the worst team in the league that season.
Sharp put up 0.63ppg with the Stanley Cup Champions. The top
2 forwards he played with at even strength were Brad Richards and Patrick Kane. Followed closely by Andrew Shaw and Marian Hossa. That's pretty good company.
While Sharp has no where close to the trade value of Carter, often players on lesser teams can better scoring icetime than players on elite teams.
Chicago spreads their PP and premium ice time around. Players need to be defensively responsible.
Players like Kessel on Toronto get unlimited time to float around and worry only about offense.
Sharp is an excellent 3-zone player, great on the PP and a superb penalty killer. He was a valuable forward to the Olympic team just a few years ago. Whatever team he goes to will get a couple of excellent years from him. He might just be the missing link to helping a bubble team make the play-offs, or make that near contender an actual contender.
Who else is available that you can honestly say those types of things about?
No one.
His trade value is severly underrated in a market starved for a complate player.