In this Forgotten Weapons video Ian had talked about designing a "modern frontier rifle". In my opinion, the SKS fits that roll quite nicely. It's cheap, ammo's cheap. Its sturdy, simple, easy to fire, easy to clean (once you get the cosmoline out of it). It uses an internal magazine with stripper clips, which I find superior to box mags for lower capacities.
I mean, it ticks all the boxes for an all-purpose, jack of all trades rifle.
Yup, the only thing you left out, is they are cheap because millions of them were dumped into surplus markets, that were already flooded with all sorts of other offerings.
My first SKS cost me $49.95 if I bought 6 of them, which I did. Ammo was tough to come by for a few years.
If the SKS were to be manufactured today, to the same standards as the present surplus rifles, they wouldn't be nearly as cheap as they are now. Even the price of surplus models has doubled or more, depending on condition and lots of other factors. I never thought I would see a Yugo 59/66 at $800