I think that the price variations in double guns are more minor, and subject to the general feelings about the economy. At least this is how it appears to me, from going to gun shows and auctions.

I think military firearm prices are more subject to generational changes. It seems to me that the WW2 firearms have dropped significantly (M1, M1 carbine, etc.) as now the preference has shifted to the more modern AR types. Those have gone up significantly, although Second Amendment issues probably play a part as well.

I prefer wood to plastic, leather to nylon, waxed cotton to Gore-Tex, and split bamboo to graphite.