I shipped a box of items to myself to Boardwalk Villas from the office. Shipped it two-day shipping using my Firm's account. It was less than $20 to ship.
Sent this very same box back home via the Conference Center at the Boardwalk and used my own shipping label, box, sealed it myself, etc., and when I got the charge for the returned box -- it was more than double what I paid for it to go to WDW. I'm guessing Disney felt the need to add on their own shipping costs to the package -- not that they did anything other than pass the box off to the local Federal Express driver.
Not sure if this is the experience from all Disney resorts or just those with conference centers. But I know I'll never ship a box back home via Fedex using the conference center again.