The article says:
" at the cost of their No. 8 pick, matching salary necessary to absorb Kent Bazemore’s bloated contract, and perhaps another asset."
It all depends on what that vaguely phrased "other asset" was.
Anyway, I assume lots of teams were making offers and the Hawks were willing to sell at a relatively low price. The Cavs were just unlucky (regardless of whom they would have drafted , it's rare that a nr 3 pick gets traded for a bargain price).