That's the NET trade-off.
Now say you do in fact trade Fowler for that coveted young, cost-controlled, ready-now top-6 forward. How do you protect him at the draft ?
The Ducks all already rumored to go 8+1, right ? Perry, Getzlaf, Kesler and Bieksa MUST be protected. Lindholm and Vatanen will be for sure. That leaves two spots for Rakell, Silfverberg, Fowler and Despres...not even counting Cogliano.
You trade Fowler for that cost-controlled ready-now top-6 winger. And then what ? You keep your newly acquired top-6 winger and probably Despres...and then lose Rakell or Silfverberg ? Now you don't have Fowler, and you're back to square 1 with a hole in your top-6/top-9.
Now I'm not saying this means the Ducks should undeniably go for a package of prospects like the one I suggested. However, this is an option the Ducks could (and maybe should) evaluate.
The thing is, the closer we'll get to the expansion draft, the weaker the offers are going to get. Like I said in my original post, this isn't even a price I would be comfortable to pay for Fowler RIGHT NOW. The Habs NEED those young players, and while getting Fowler would be quite a nice addition, it would also mean leaving Beaulieu unprotected. But that trade would make a lot more sense for the Ducks, all things considered.