Reply to D4Doug:
In 1953, My dad bought my D4 7U equiped with a dozer for $11,000.
I don't have any American price lists from the late 1930's .. but I do have a 1938 Australian price list for new, bare agricultural Cats from the dealer in Melbourne, Victoria, Australia.
The price of a 40" gauge D2 in July 1938 was AU£695 (one Aust. Pound = approx US$4.00 in 193😎 .. and the 50" gauge D2 was AU£720.
This makes the two tractors approximately US$2780 and $2880 approximately, in Australia, in July 1938.
Deducting shipping costs from the U.S. (probably about US$350-US$400) indicates the sale price of the D2 in the U.S. in 1938 would have been in the region of US$2400-$2500.
I don't think there was a lot of variation in pricing between 1938 and 1946 due to Wartime price controls, which kept a lid on any price increases.
The sale price of a D2 in Australia in 1938, equated approximately to double the selling price of a new 6 cyl, 1938 Chevrolet sedan. Maybe that will give you some perception of values for the era. Passenger cars in the U.S. would have been cheaper overall at that time, compared to Australia, due to efficiencies in the scale of production and distribution.
1938 Caterpillar price list (Melbourne, Australia) ..
http://img265.imageshack.us/img265/8981/1938catpricelistli6.jpg
(the print is fuzzy in the scan, because the original is fuzzy, due to a poor quality typewriter ribbon) ..