I have sold several b bags on ebay. All were magenta and two of the three sold for substantially more than retail. But - all were brand new, never used. Also, the color is sold out so it's really supply and demand. Like SoCal said, white is currently available and since your bag has been used, I would be surprised it it sold close retail. I think you'll have more luck selling it if it was priced in the 800-900 range.
With that said, it is ebay so you never know. G/L selling it!