I tried the same with a low cost grill iron ( to make sandwiches 🥪). With back in my mind that I not would buy another one but fix this one once it should break. The hinge broke and a few tabs that hold oneside metal in place. I glued it but after two weeks the it broke on another place. Could not live without tosties, have now a newer bigger one...I've tried...
I think mechanical failure is different than an electrical failure. Plastic and metal breaking is harder to fix than the electrical for a grill, which shouldn't be much more than a power cord, a resistor dial, a switch, and a heating element.
You are right, of course. Also repetitive thermal expansion comes into play here. We can compare it with repairing a broken heating element or other single part, instead of replacing it. My patience to properly glue it was also part of failure, hehe.