The only way I'd trade that pick is if it got us a star under contract for multiple years... or an elite prospect like Jabari Parker, Jahlil Okafor, or D'Angelo Russell that might be better than what the pick is going to get us in the draft.
This.
I would look at the Rondo trade last year as the baseline for trading for a rental fringe all star. We got back Wright, Nelson, Crowder(not what he is now), a protected first, and a second.
So I think we could get away with something like this.
Lee, JJ, Zeller, Dallas first, and the Minny second for Howard and Harrell.
Amir, Sully, Hunter, our first, philly's second for Horford.
You could even make the argument that's a slight overpay based on the Rondo trade but something like that I would look at.