Beatles demo sold on eBay for £3,400

I notice that a demo copy of the Beatles' first single Love me do sold for £3,400 on eBay the other day. Now I sell records on eBay all the time (well over 600 to date - mostly UK stuff that I don't want) but I've never even got close to the selling price of this 45. The best I've done so far is £102 - also for a demo - for Edwin Starr's Stop her on sight on Polydor. Occasionally if the bidding gets hot I can get up to £40 or £50, but mostly the records I sell go for a few quid. It earns me a couple of hundred quid a month which is fine, considering that most of them are bought from boot sales or charity shops for a pound or so. But the Beatles record got me thinking about demos and what they are worth. These days demos appear to be deliberately released as collectors' items, but back in the 50s and 60s demos were a limited run (usually 250 or 500) of advanced copies for DJs, record reviewers etc usually on a white label with a large A on the hit side, or different coloured labels (orange (initially one sided only) or yellow for London, dark green for RCA etc) from normal releases. I reviewed records for the Croydon Advertiser in the mid 60s and still have some of the original demo copies I was sent. Collectors will pay a huge premium for a demo by a band like the Beatles, and for collectable labels like Tamla Motown. But often the demo is more common than the standard release for a record that sank without trace. The Rare Record Guide - the vinyl collector's Bible - does an excellent job at valuing standard releases (even if many of the values are much higher than you are likely to get on eBay) but gives no guidance on the value of demos. What vinyl freaks like me, with quite a few demos in my collection, mostly 45s but also some LPs, need is a guide to what they are worth compared with standard issues. Maybe a whole new guide is the answer.