With median income sitting at $146,827, a chain-drive unit gets swapped for a belt-drive without much debate - quieter operation matters more here than shaving cost off the invoice. We don't post a number for the job here because door weight, header clearance, and whether you need a new bracket all change the total, and guessing at a price before we've seen the door does nobody favors. What we can tell you is the honest limitation: if your existing rail or bracket is undersized for a heavier door, replacing just the motor head is a false economy - you'll be back to a strained unit within a couple of years. We'd rather quote the bracket upgrade up front than have you pay for the same fix twice.