What do Columbus get in return?
Last time a star #1 goalie was traded as a rental was Ryan Miller (IIRC) in 13-14. At the time of the trade he was around the top of the league in save % and had 5 consecutive seasons prior above 91.5%.
Sabres paired him with Steve Ott (at the time high character 30ish point forward) and send those two to the Blues for pending FA Jaro Halak, 1 year of Chris Stewart (top 9 W), prospect William Carrier (bottom 6 future), a late first round pick and a 3rd rounder.
Stewart and Halak made a combined ~7.8M and Miller had a 6.2M cap hit so it was basically about moving salary and sending back a goalie who can play for Buffalo.
So essentially late 1st, okay prospect and a 3rd. But Ott also had value, and Miller was having a terrific season, complete opposite from Bob. I also remember because the Sabres defense was seen as a bad one that worked in Miller's favor even more. Funny enough, he goes to the strong defensive team in the Blues and his numbers were trash the rest of the way and the Blues lost in the 1st round to Chicago. LA won the cup.
I think that gives a pretty good idea of what a trade involving Bob could look like. No high-end pieces to Columbus. A late 1st + prospect + work out the cap technicalities is probably realistic. Or maybe 2x 2nd's or something along those lines.
However Bob's NMC complicates things and we don't know where he'd be willing to go. Not to mention im not sure if the 1st place Metro Jackets would even trade Bob for those assets. Korpi has been all flashes so far his career and it's not like the Jackets desperately need more prospects.