Because QVC, like virtually all other retailers, doesn't get as much of a bulk shipping discount on items that are lightweight, so it basically charges customers what it gets charged because shipping fees are part of its revenue model. On larger items, a larger discount can be passed along, so the overall shipping charge is typically quite low. This is why I usually think it's silly for customers to complain about shipping fees—of course none of us wants to pay for shipping at all, but for a regular person to ship a piece of jewelry, we'd pay what QVC charges, and for a regular person to ship a comforter or another large bulky item, it would cost a lot more. For example, there's no way you're getting a ladder or a set of stoneware or an ottoman home for $5.50-$7.50.
(As another example, I wanted to return some bedding to the Q because I didn't like the design, and I thought I'd just pay for it myself instead of using their label and having the fee deducted . . . until I discovered that instead of the $10.95 label fee, I'd be paying almost $20!)