Comparing apples to apples, I’d say a $21 budget would be about right. Arguably, KD and Steph would be $6 players, Klay and Draymond $4, and Iggy $1.
With the $15 budget, the answer to the original question would absolutely be no, GSW would not be beat.
My best $21 lineup:
Now that would be a game made for prime time!