Typically a professional cage will cost you $100 per "point" for an NHRA legal cage. So a 6 point cage is $600. That's for mild steel, for chromolly, it will be a good bit more.

Come to think of it, with the steel shortage and price gauging going on right now, it's probably going to be more expensive than that. Unless you need it right now, I'd wait until the prices cool off.