The No1 was Bill Rugers pet project and HALO product - the one that showed the best of Ruger skill at arms making. Great engineering, great workmanship, fit and finish, Great wood. Unfortunately not the case in the last several years.
They were always low production increasing rarity. The production wasn't "limited" to increase cost but due to demand. Spreading engineering, tooling, assembly, advertising etc over a limited number of guns increases cost.
Lots of little things made them expensive to build/sell and today they have held their value. Possibly due to the fact that most are still pristine having been shot very little. All of mine were bought used and are 95-100% ranging from my first one a black pad RSI with a couple small dings in the stock to my red pad 1A which was NIB when I got it last year.
I've got one of each type and of course don't shoot them regularly. Will I buy more? Maybe I'm looking for a stainless just to round out the set. Any others I add will need to have red butt pads as I consider them to be superior in quality to the later ones.
I got my first one the RSI on a trade for my Remington XP100. Then started doing my homework and all the rest are earlier red pad ones.