Well, if the insides look like this:
https://pcpartpicker.com/product/Pm4gXL/thermaltake-case-ca1b300m1nn00
Then you can maybe ask $15-20. Just an older design and you can get them from practically any company.
If it doesn't look like that, we'll need to see the insides and the side to get a better idea.
Thermaltake has been around a long time, and they've made probably thousands of models at this point. They usually change up the external styling every few years