The most expensive case I owned was probably the mophie battery case for my iPhone 4 which was probably around $60 at the time. The otterbox cases were also one of my expensive cases, including LifeProof cases which were normally around $45-50.
The cheapest case I bought was also for my iPhone 4 and it was Speck's 'Batwell Candy shell' in the cotton dandy blue color for $24 on Amazon. I was obsessed with the color back in high school. Those were the days. haha.