so doing some math on this challenge assuming you do C&P bookings and you are eligible for one of the hyatt summer sweet dreams sweet rewards promotions that give 30k bonus points with 15 stays:
Point Cost:
Stay 15 nights x -2500HGP = -37500
-37500 + 20%(7500) refund for point bookings as cc holder till 7/31 (if u were targeted) = -30000
-30000 + 30000 for 15 night promotion = 0
0 + 6000(1000 points per first six stays) = 6000
6000 + 3750 + 560(base points + plat bonus points earned on $750 spend) = 10310 earned after 15 stays (actually a tiny drop more since the last 3 you will have diamond status)
Still a $750 cost, but thats now lessened a bit with ~10k points as well as diamond benefits. or without cc promo its still not costing you on the points end. Seems like this could be worth it especially if you have good use for the suite upgrades down the road.