Interesting post, MJR.
It sent me scurring into the basement to look for my
1980 Gun Digest. I figured that I could infer some information from the catalog in the back that would be contemporaneous to the guns your "fourth-rate gunsmith" and technical advisor at the NRA were talking about.
I decided to compare an M10 to an M13, both with Heavy Barrels, since they are very similar except for what they will chamber. Well, the weight of each is given as 34 oz. so no help there. Of course, the weights could be approximate... or even incorrect.
The price for the M10 HB was $125.50 while the M13 sold for $139.00. That's about a 10% difference. This reinforces the notion that a higher quality of steel was used for the M13 and / or that the heat-treating required more time and labor, hence the higher price. Or it may mean that S&W just sold a whole lot more M10s so they could give a price break on them.
Anyway, second the motion to ask Mr. Jinks.