Just found this boxed C5 on eBay with a starting bid of £1,500. It may also explain why the front wheel shrouds are often missing - owners not bothering to put them on when they were new as they came bubble wrapped separately?
http://www.ebay.co.uk/itm/SINCLAIR-C5-BRAND-NEW-IN-FACTORY-BOX-/120933987226?pt=UK_Collectables_Vintage_RL&hash=item1c283a339a
Never ceases to amaze me just how many of these boxed new ones keep cropping up - I've had two myself over the years ;D
The novelty wears off after a while :P
Just my humble opinion but I think it is far more enjoyable riding about on one you've restored ourself .