The DCM (predecessor of the CMP) blew thousands of them out in the late 1950's - early 1960's, at ridiculously low prices (less than $20, as I recall). At the time, you had to be an NRA member to buy from the DCM, so this was a huge recruiting tool for the NRA. Along with carbines, the DCM was selling Springfields, Enfields, and M1911's. They were not selling Garands except for NM versions, and there was a one-in-a-lifetime limit on those. To buy a Garand, you had to submit a competitive scorecard among other things. In comparison, carbines were easy to get.
The government was eager to surplus the carbines in the 1950's. Millions were produced in WW2, with the idea of arming rear-area and support troops (not first-line infantry) with something that was easier to use than a pistol. The doctrine for employing carbines seems to have been revisited after the war. I remember that when the M14 was adopted in the mid-1950's, it was touted as the universal replacement for the M1 Garand, the carbine, the BAR, and other weapons (it didn't quite work out that way). In terms of its employment, the idea of the carbine was a doctrinal dead end. Anyway, the advent of the M16 made all these discussions moot.
