I know the location has now changed for the shuttle, so not sure how much further that is from the resorts, so how much more cab fare would be.
Last year, we were at POFQ, took a cab to the Premium Outlets where the shuttle picked up. It was $5 per person round trip for the shuttle. And about $20 with tip each way for the cab. So our family of four, it cost about $60.
We looked into a one-day car rental on property, too, and found the cost to be just about the same. We decided the cab/shuttle route was just more convenient for us.
It was super easy and I didn't think very expensive at all. The shuttle is one of those large, comfy buses and they show movies along the way (kind of like DME!).