Quoting: Ragsandbluesfan
Thats not enough for hayes
A good trade comparison would be Evander Kane last year. Similar age, similar production, both UFA's, Kane would have been probably a bit more valuable as he had been a bit more productive, on a bad team. As a rental, San Jose gave up a late 1st, and conditional 4th that became a 1st if Kane re-signed, and Dan O'Regan, a 24 year old former 5th round pick, who might end up as a depth forward at best.
Given what San Jose gave up for Kane, I wouldn't say that Hayes would be worth much more than I've listed (maybe switch a 2nd for a 1st if he re-signs). 2 second round picks are really good draft capital, Jon Gillies is a BIG, well regarded goalie prospect, and Mangiapane is a scoring machine, that has scored at every level he's played at. He could figure to be a potential top-6 forward if he pans out.
All that being said, Hayes is a rental, and GM's have really smartened up over the last few years.