One fascinating aspect of the hobby of collecting camera that span over three centuries and in may respects have not changed in fundamental design over that period is working out:-
Although some collectors have claimed that they have 6000 and more cameras as an investment this is likely to be a folly. The Minox A was originally sold for 139USD (1949: 3.69USD ~ 1GBP) and has achieved that steadily second hand over a number of years. The purchasing power of 139USD in 1949 is equivalent to about 1074USD in 2003, or roughly the purchase price of a Minox TLX. Riga cameras are considered rare and have been sold in London for 4000GBP (1996) but now even the USSR engraved camera can be purchased for under 3000USD (2004) - a third. Near mint and complete always gets a premium but for many subminiature cameras you may find that a film cassette will sell for more than the camera but even these sell for anything from 5USD to 35USD in the same month. There is also a wide difference in the selling price of cameras in different countries,. where, for Minox equipment 1DEM= 1USD = 1GBP when exchange rates have been more typically 4:2:1 which can only be partially attributed to different sales tax rates.
Current Value of Old Money list many interesting links to look for this information.
EH.Net calculator for comparing the purchasing power of money in the United States (or colonies) from 1665 to any other year including the present (Purchasing Power of the Dollar, 1665 - Present).
Gold price compared the US$ or Price of Gold
Comparing Historical exchange rates
From Oanda FXTrade, largest foreign exchange database on the Internet. You select the two currencies and the amount and you can ask for different rates (Interbank, Typical Credit Card, Typical Cash Rate). Also you can ask for today's rate or for any day since 1/1/1990
Pacific Policy Analysis Computing & Information Facilty in Commerce Exchange Rate Service, provided by Prof. Werner Antweiler University of British Columbia, Vancouver, Canada provides:-
Historic Annual Average Rates 1948-2002 (PDF)
What is Purchasing Power Parity? - Facts and Figures
As of 8th July 2003: buying EUR 1.3921EUR=1GBP, selling EUR 1.5432EUR=1GBP. buying USD 1.5883USD=1GBP, selling USD 1.7611USD=1GBP (1.14USD=1EUR) subject to change
Current exchanges rates can be found at Bloomberg, Thomas Cook, Yahoo and Oanda. To buy currency few sites quote both buying and selling rates, but Oanda gives a quote to buy foreign currency (including GBP) in US$ at http://www.oanda.com/products/fxdelivery/. Also NatWest gives a buying and selling quote from the menu options "Our Account & Service / Travel / Exchange Rates" or using the Currency Converter . The Royal Mail also has a currency converter and charge no commission.