Yeah, you can definitely save $$$$ buying components separately (I don't though -- too lazy).

20mg ephedrine, 200 caffeine, and 325 aspirin are the recommended amounts.

Also, green tea extract has shown to have some synergistic action with ephedrine....the research on this is limited but promising. They attribute the benefits to catechin polyphenols found in green tea. Anyway, I think they're worthy of becoming the 4th member of the stack (or replace aspirin, as it's redundant - caffeine and aspirin both being methylzanthines).

Again....my $0.02