A nice set of 5 with good centers and bands usually goes for around $375. You'll find good bands are hard to find; they tend to get road-rashed, and they're only found on SSIV and the 77-79 big car N98 chrome wheel option.
Most guys running them have found early 90s Chev/GMC truck trim bands to be a good substitute, and those are common as dirt. They fit into the rim recess right, and aren't as picky about wheel weight locations as the true SSIV bands either.
Every 70s big car I've owned has eventually had a set. The Ninety Eight is wearing a real nice set now- a big guy in dancing shoes! They were usually found on Delta Royale coupes, but put a set on a 4-door hardtop and watch the whole character of the car change.
I like the SSIV design so much that I have a set on my 74 Hurst- not real SSIV, but the original Motor Wheel Exiter which is where the SSIV design came from. MW made the Polycast wheels for Olds and Pontiac, and later Ford. Difference is center cap and it uses no trim ring. 80s FWD Cutlass SSIII center caps fit those wheels like they were made for them, and SSI repop Rocket emblems fit those center caps perfectly. I often refer to them as "Hurst Experimental Wheels" when I have the car out at a local show; these locals don't know the difference.
I bought the set of four NOS Exiters from a Mustang vendor at Fall Carlisle around 2003, for a total of $40.00. They were GM 5x4-3/4 bolt pattern, so they were no use to him. He had ten, and if I hadn't been on that stupid Bravada I'd have brought all ten home. I think that trip was when I first realised what Bob Brannan meant when he told me "Make sure it fits you", and that I didn't like that truck.