Well, eBay has caused, that the prices for such stuff were collapsed in the last 10 years. Some idiots on spare parts markets ask ridicoulous prices, but in fact the collector's prices for repair manuals, instruction manuals and sales brochures for cars are much lower than in the pre-internet-times.
This one is totally overpriced http://www.ebay.de/itm/Reparaturanleitung-VW-K-70-L-S-LS-K70-Jetzt-helfe-ich-mir-selbst-/380590815328?pt=Sach_Fachbücher&hash=item589cfaf860
As the issue for the Fiat 500 it shall be the rarest manual of the whole series. In the 90ies they have cost around 40 to 50 D-Mark (ca.20-30 €) and were really hard to get, while the issues for the NSU Prinz and Audi 60 were to find everywhere.
Nowadays the realistic price for it is around 10-15€, depending on the condition. I've also catched some for 5 to 7€.

The hardest price-collaps was for that: http://www.ebay.de/itm/7-RAINER-GUNZLER-ZDF-Auto-Tester-der-60er-Jahre-testet-den-Volkswagen-VW-K-70-/190802845178?pt=Bücher_Unterhaltung_Music_CDs&hash=item2c6cbc5dfa (extremely overpriced here). In the 90ies it cost minimum 30 D-Mark (15 €) but nowadays you cannot sell it at eBay for even 2 or 3€.

Of course, very unique special goodies can get incredibvle prices at eBay, but that common, serially produced stuff as this kind of literature is definitely cheaper nowadays.
But there are still moron of sellers on spare parts markets, who still haven't realised that