ChipFlip
Four full-size cases sit within $15 of each other in ChipFlip's tracked used listings right now, $135 to $150. At that tight a spread, the differences that actually matter aren't obvious from price alone.
Full tower doesn't mean the same thing across brands
The Lian Li O11 Dynamic EVO XL and the Fractal Design Define 7 XL are both full towers, and both track close to $150 used. But they're built for different priorities. The Lian Li leans into showcase-style builds with heavy glass panels and a layout meant to be seen. The Fractal leans toward quiet, dampened panels built for someone who wants the PC to disappear into the background, not be a centerpiece.
Mid tower still holds real value here
The Cooler Master HAF 922 at $150 and the Fractal Design Define C at $149.99 both sit in mid-tower territory at essentially the same price as the full towers above. If you don't need the extra internal volume a full tower provides, paying the same price for less case doesn't make sense unless a specific feature on the mid tower is worth it to you.
What justifies picking one over another
Airflow versus noise dampening is the real fork in the road. A case built around mesh panels and open airflow keeps components cooler under load but runs louder. A case built around solid, dampened panels runs quieter but needs better internal fan planning to avoid trapping heat. Check which design philosophy a listing follows before assuming "full tower" tells you everything you need to know.
Buying a case used
Cases carry less risk than most PC parts since there's nothing electronic to fail. The real things to check: bent or missing standoffs, working fan headers and front-panel connectors, and glass panels free of cracks or deep scratches. A dented panel is cosmetic. A missing standoff means extra work during the build.
Bottom line
At this tight a price cluster, don't pick a case on size alone. Match the airflow-versus-noise tradeoff to how you'll really use the machine, and let that decide it.