He's our hardest working player, but at a position we have a logjam at, and he's expiring and will probably get a bigger contract offer than people expect. It makes sense to capitalize on his value.
I think that Boston's 2018 pick is a good deal for both teams. BOS doesn't have to trade back any salary because they have an Injury Exception for Gordon Hayward with which they can take in an expiring contract that's worth up to $8M via trade.
With Boston's pick, we could add someone like Kyle Kuzma, Jordan Bell, or Malcolm Brogdon. Either get Bostons 2018 pick or the better pick of MEM's/LAC's in 2019.