Just kind of curious why they are >> $100 to replace. Sure they have a tiny bit of smarts but an Arduino is < $20 and a relay board is like $40. I guess getting the certifications isn't exactly cheap...
Law of supply and demand, low demand specialty item gets expensive. They can also charge what they want. Kind of like gas, you can't go without it so you pony up what they want to get it because there is no other option.