I actually own a 4'x2' plastic cage from PetSmart, but I think it was $80-90 (I had to order it online, it wasn't available in store). Lots of people hate the pet store cages, but I actually like it. I can feed my bun in there, keep his litter box in there, etc, and it keeps all of his mess contained to one small plastic area that I can wipe clean. My bun loves to go in his cage and sit up on the shelf or hide under it. I also got him an exercise pen to attach to the front of the cage. At first he stayed in the cage and was let out to play in the pen, but once we realized he had the litter box thing down, he got the whole cage plus xpen area as his cage (which is 4'x8' total).
I think NIC cages are great, but I love my cage set up because it's simple and very easy to clean. Plus, I can take down the xpen if we have guests over, or if I need to take my bun somewhere I can just fold up the xpen and bring that along, instead of needing to drag a whole cage somewhere. Xpens are great! If I had to give up either my pet store cage or my xpen, I would absolutely give up the cage and keep the xpen as his entire living area.