Some variants of the SKS might be worth "collecting". Run of the mill SKS rifles are worth owning and shooting if you like owning and shooting that kind of gun, but they aren't really worth "collecting", IMO.
In the early 1990s, before Clinton stopped the import of most Chinese small arms and ammunition, you could still buy new Chinese SKS rifles and 500 rounds of new Chinese 7.62x39 ammo for less than $100 before tax. There was a pawnshop near where I worked at the time and their regular retail price was $49.95 for the rifle and 10 cents a round for the ammo....when I was in high school a surplus SKS Rifle & 1200 rounds ammo was $89.