I bought one of the first M1A's on the market (1973, made in Devine, Texas, serial number under 1,000). I paid what was for me, then, the princely sum of $250. I still have the gun (upgraded in several ways).
The reason I bought it was that I was, and still am, a collector of U.S. military weapons. This was my stand-in for the M14.
If you're not a serious collector, my advice is not to get an M1A. If you want a .308 for practical use, get an AR-10, FAL, or PTR (G3 clone). (Of these, the FAL is my favorite. It exudes class.)