James Cameron has a history of making great things happen with a low budget, and spending millions responsibly to actually make a positive difference in big budget films.

is a “B-movie” now?

Did you not read the article? It was regarded as a B-movie when it came out: a low-budget sci-fi slasher/horror film. Arnold referred to it as a B-movie when asked about it on the set of Conan the Barbarian (which had 3 times the budget as Terminator). The New York Times referred to it as a B-movie in its review, as discussed by this article, which is also why the headline uses quotes around “B-movie.”