Burned electrical lines!!!! oh my!!!!

Well we came home last night to find a weird burning smell. Well my Rono checked all the heaters and while I watched I was looking at the thermostat. Well saw brown marks on the wall. Come to realize the wires all burned up in the thermostat. Called the electrician to come out. 24 hours later and 192 dollars we got a new thermostat. Wow emergency visits can be very expensive.