What? A 4x2" reducing coupling costs under 5 bucks, (four something), at my hardware store. If you're ordering off McMaster, they will be expensive. Note that reducing couplings are DWV, (unrated for water pressure), and are not to be used on pneumatics. Only combustions are safe with them.
EDIT: well, nevermind, that's why they're 70 bucks. Okay, let me rephrase that, "Cheap reducing couplings are DWV, and are not to be used in pneumatics, as they are only safe for combustions..."