Hi everyone - I'm now back from a day out and can join in the fun.
Chris - it's nice to see the 1928 and 1938 Marples catalogues getting known and used more widely. I was lucky enough to buy them both for very reasonable prices and scanned them because there is so much useful information in them - they deserve a wide readership.
A few extra points:
Within a single catalogue it's safe to look at relative prices and see that, for example, parallel irons cost 50% more than tapered. But these two catalogues were wholesale catalogues, issued to trade customers. Most would have been businesses with retail shops but I expect big operations such as railway companies would also have dealt direct. The clue is that most items were priced in dozens. An ordinary user would not want to buy a dozen plane irons and would not have been able to. There's also a reference in the introduction to Marples' "many trade friends".
Even then, the printed prices would not have been the actual prices paid by most customers. It was normal to issue extra sheets showing discounts or plussages to be applied to the printed prices. These would vary across different customers - the best customers got the best deal - and across time, so an old printed list could still provide a 'base' price for calculating current prices for a decade or more. (It was even possible for a plussage and one or more discounts to be applied at the same time, making the calculations complicated fun. I remember this as still being current practice when I worked as a buyer in the 1980s.)
Some catalogues were issued to end users and gave retail prices for single tools or were unpriced.
We are fortunate in that a great many old catalogues have been preserved - the Hawley Collection has thousands - though prices paid by collectors for the few that come to market seem to be rising fast. So for most of us, the answer lies in scanned versions.
Some of these are freely available, others less so.
If you want to look further back, scans of quite a lot of catalogues - including Marples in 1903 and 1921 - are available from TATHS. You can buy them on CD in their shop here -
http://www.taths.org.uk/shop - you will want CD no 3. Alternatively, if you sign up as a member, you can download most of these catalogues for free.