It looks like Amazon has some sort of sale on few higher end Delta items, including some of their dust collectors:
50-763 3 HP single phase: $336.69
50-765 5 HP single phase: $694.46
50-762 3 HP 3-phase: $400.64
50-764 5 HP 3-phase: $486.65
These prices are before the $50 off $300 discount and...