I found the difference
You two don't know what you're talking about. Those answers are made-up. I compared the cases physically in-store. The difference is that the $99.99 case does NOT have a backlit keyboard, regardless of what is stated here. The $139.99 case DOES have a backlit keyboard. Those other two reviews are for the wrong case as well. Same build quality. If you buy the THZ500US case and are expecting a backlit keyboard, you will be highly disappointed. The description for the THZ500US is flat out wrong! There's no Ni-Cad battery either. Both have Lithium-Ion batteries.