considering its the slimline version, which still sells new here in the UK for a good £99, plus it's silver, which seems to add an extra £10 to the price for little or no reason, I'd say its worth a good £50 if you trade it in to a reputable games store, or 143550 Ugandan Shillings.
...and with that post, people of Britain were so surprised that "tea was spilled, crumpets were dropped and monocles everywhere popped out in shock."