Prime offers benefits far beyond just shipping. Benefits that make subscriptions worth it for people that don't necessarily purchase items from Amazon. There's no comparison between what Amazon does and QVC.
And I find QVC's shipping on par with many other retailers. I placed an order yesterday with a company that didn't have items I wanted in their brick and mortar location. My estimated delivery date is in two weeks. I find QVC's delivery dates to be dependent on whether it comes from their warehouse or a vendor.