There's two things to consider here:
1) The U.S. military issued M1 Carbines made by a variety of companies -- Inland Manufacturing (a subsidiary of GM) made the largest batch, but Winchester, Saginaw Gear (also GM), National Postal Meter, Underwood Typewriter, Quality Hardware, IBM, Standard Products, and Rock-Ola Jukebox company all made several hundred thousand. They are all just fine guns and many are highly sought-after by collectors.
Considering that until recently the CMP was still selling surplus real M1 Carbines for a bit over $500, you can probably find one for that if you're patient and keep your eyes open for a few months.
2) There have been a few commercial gun makers who turned out lesser copies of the Carbine. Iver Johnson and Plainfield are brands you might see for cheap, and some say that they are not too bad. "Universal" was another maker and they probably should be avoided. These are not exact copies and aren't worth much at all.
Auto-Ordinance also now makes some very nice Carbine copies, but they are (justifiably, I guess) very expensive.