If you swap Kahkonen with Hill, then Sharks accept. Sharks see Kahkonen as their long-term 1A and they can add an additional piece on top of Hill like a depth winger or a goalie prospect to make it with Toronto's while.

What type of return would the Sharks be looking for just Adin Hill?

Not going anywhere with that goaltending

For Hill alone a 3rd to 4th round pick would be fair value. If we were to add a goalie prospect (like Sawchenko or Gaudreau) or a depth player, then the original trade would be a fit.