Is this reasonable

No

No. Why are the Leafs trading so many young assets just to get good goalie. Just sign Campbelll at 5.25, buy at Mrzarek at an average of 1.2m.....geez the Leafs just as good in net and keep those no cap assets.
And really look at that roster....5.5m for 7 more players....hardly cap efficient.

Too much for the Leafs to give up but it isnt enough to make the Ducks consider moving Gibson let alone Comtois too

As @palhal says, paying Campbell around 5M AAV and buying out Mrazek would be much more efficient for the Leafs

if the leafs are giving that up, they are going to get a goalie who can put up at least league average numbers

Anaheim isn't trading Comtois except to a team that will overpay for him.

If the Ducks decide to move on from Gibson they will want quite a bit, the Leafs might be willing to move Robertson and some picks for him at most. They need Sandin or how will they ever get a solid D-core to play in front of their goalie? If they all stay Matthews, Marner, and Nylander will get raises, probably take more % of the cap each than when they signed. Tavares will get paid less but the savings from his contract will mostly go to their raises.