Maybe because prior to 1968 you could get a Springfield for less than $40, while an Argentine Mauser went for less than $20, through the mail. My first '06 was a sporterized 1903-A3 from Klein Sporting Goods (in Chicago, if memory serves me) bought via the USPS for $60. That had a nice Monte Carlo stock, turned down barrel, sporting sights and was drilled & tapped for scope mounts. This when the MSRP for Winchester 94 or Marlin 336 was $87.50, and the Winchester model 70 and Remington 700 BDL went for $149. And I bought a Remington Rolling Block in .43 Egyptian for $7.50.... There were lots more foreign guns available than American, and the price was set to reflect this fact.
-WH-