The "cost" of basic commodities like steel do not really change much over the years, because they are relatively plentiful, and we have an established technological infrastructure worldwide to mine, process, and machine them...
The "value" of the US$ however, is a VERY different story. Since it is a fiat currency, backed by nothing more than good faith in the credit of the US Treasury, it is subject to manipulation by the Federal reserve, through the issuing of more curency, manipulating the interest rates, and changing the laws that regulate fractional reserve lending practices, derivatives, and international currency speculation.
One ounce of gold would by a pretty nice outfit made of gold-shot linen for a member of Egyptian nobility int he days of the Pharaohs.
One ounce of gold, in Elizabethan England could buy a nice doublet, slops, hose, shirt, and cap at a fine tailor in London.
One ounce of gold would today--at any fine clothier in the US--buy you a REALLY nice men's suit.
A similar parallel exists between mid-priced handguns and a half-ounce of gold. You could go back to the old "Navy Colt" revolvers, up to today--a half oz of gold will buy you a nice, mid-priced handgun--and has always been thus since handguns were first mass-produced.
The VALUE of gold (and many raw materials) never changes--it ALWAYS purchases the same amount of goods--throughout the history of man. (with a few anomalous spikes here and there).
But the VALUE of a US $ has been nose-diving for nearly a century, and essentially reached "terminal velocity" sometime in "2009".
The "price" of firearms has NOT gone up. The purchasing power of the dollar has plummetted, which is relfected in higher "prices"...
So no, the cost of firearms hasn't doubled.
The purchasing power of the US$ has fallen by half.
And those two things are VERY different, and mean VERY different things, in terms of socio-economics...