According to my research, the more expensive model is an exclusive "Tempered Glass Edition":

The Thermaltake Level 20 Tempered Glass Edition is the flagship model, exclusively available for Thermaltake's 20th anniversary. The Super Tower case is equipped with Trio-Chamber design, tempered glass and tool-free locking mechanism, fast connections (USB-C 3.2 and USB-A 3.2), TT Premium Gaming PCIe 3.0 riser cable and three pre-installed Riing Plus 14 LED RGB fans, 2 Lumi Plus LED strips and 1x Riing Plus Digital Controller. The Level 20 Tempered Glass Edition is the ultimate gaming case for all gamers and enthusiasts.

The other item is the "Thermaltake Level 20 RS ARGB" case:

The Thermaltake Level 20 RS ARGB is an ATX midi tower case with two tempered glass side panels. Two pre-installed 200 mm 5V ARGB front fans and a 120 mm standard fan ensure good cooling of the components.

I have reported that the cases should be listed separately in the shop.