They're certainly a lot cheaper than a similar condition US Colt would be. They're confused a lot with the Balister Molina 1911s which were also made in Argentina but were knocks offs and of lower quality. I've had my eye out for a Sistema for a while, as they seem to be a good value, although they were cheaper a few years ago before everybody "discovered" them. I usually see them now in good shape going for around $400-$500.
I have one and would definitely recommend them. As long as it is in good shape it would be a good purchase. I think like any good gun the prices are going up so it's probably best to get one now. This is my early 50's model.