It's called known/proven quality vs. zero guarantees, and that's what you pay for because that's rare and hard to get.
I mean sure, everyone would prefer to get talent for cheaper but in terms of bust probabilityyou can't compare a 3 time all star with an unproven kid with zero NBA games . Not even discussing the pertinence of the trade in itself, ... you knever know about chemistry and a ship is never guaranteed, but Trae Youbg IS already an NBA star, a 20 & 10 guy who would come as such from day 1 in SA. there's no bust possibilty as far as what he brings is concerned. On the other side, we have no real idea of what Dilly is gonna become or if is even a starter...There IS a bust probability with him... Sure, it cost you less but at the end of the day, you lose another two years and still don't have your quality PG if he busts...
I mean, there would neve be any trade for stars otherwise.