When prices are going up, some remember what we paid for a particular piece and tend to hold on to those heading towards serious dollars. Ruger Old Armies, in particular, have taken a huge jump but seem to have levelled off. Been fooling with buying/trading over 60 years.
Price jumps come in spurts with a leveling off point and sometimes even go down once the demand is met. Similar to all types of investing, the man who perfects a system that works 100% of the time investing in firearms can make a fortune selling his guidebook. Nice thing about investing in guns - we have fun owning, shooting, talking to other similar-minded folks while we own them. Common shared thought among us geezers - "Sure wish I'd bought more of those (pick one) Old Armies, Colts, Brownings, etc, etc,".
Modern gun values are easier to judge b/c, after all, with minor variations - one specific model is the same as thousands exactly like every other one. One constant remains true- junk remains junk.