I agree.
Don't forget that we also get the Mavs' pick next year (only top 7 protected) and they are the 7 seed in the West right now. While they will have some cap space next year, Tyson Chandler, Rondo, Richard Jefferson, Barea, Ledo and Amare are free agents and Monta Ellis has a player option. They could easily try to reload and fall short, giving us the 13th - 15th pick.
We could pick in the lottery twice while making the playoffs! Ainge is a genius.
However, I would trade a Nets' pick for someone like Kawhi Leonard. It's a really short list, but there are a few players I would absolutely do it for.