They made quite a lot of M1s, they're around pretty widely and you can still get refurbed ones from the CMP at a price which I think is very agreeable for a what's actually a very good semi-automatic milsurp rifle, especially for its era. Try getting a Walther G43, SVT-40, or Hakim for even a third of the price of a decent M1, and those rifles are just far less shootable, the M1 is even easily available in .308 Winchester, and with the original .30-06 Springfield you can feed it high powered hunting loads assuming you've replaced the gas plug with something like a Schuster adjustable one (but don't without one).
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The M1 also has widely available surplus AND new clips, as well as various spare parts (to a degree, even in Europe), which cannot be said for those other examples, magazines for those are rare, and magazines just do not interchange freely between SVT-40 rifles, they had the same issue in production there as with the PPSh-41, sets of mags had to be paired with the gun in question.
The only other comparably practical milsurp semi-auto rifle today is the SKS, which is cheaper and has generally cheap ammunition, and while it's an overall decent rifle, I think the M1 is a lot better and a lot nicer, weighing basically the same but with better ergos and sights, with higher power and a faster reload.
Further, Fulton Armory offers brand new parts for the M1, and will offer to build a new rifle if you provide them with a receiver, even to the short Tanker style. A bit pricy, but it's there, perhaps one day, the 3D printing revolution will allow the development of replacement tooling to make new M1 and BM59 receivers.