Most watch price alerts are noise. A dealer lists a Daytona at 30k, drops it to 28k an hour later, then deletes the listing. The alert fires twice for the same phantom deal. Here is a filtering stack that actually works. Layer 1: platform normalisation Different marketplaces use different fee structures. C24 adds 6.5% to the buyer. WatchBox builds commission into the ask. Bobs is net-of-fee retail. Before you compare two prices, convert both to the same unit — buyer-out-the-door cost in your home currency. Otherwise you are comparing a net price with a gross price. Layer 2: condition matching "Unworn" on Chrono24 and "mint" on WatchBox are not the same standard. One includes the original sticker, the other means "no scratches visible in photos." Your comparison should enforce the same condition tier across listings. If you do not, you are pricing an A-grade watch against a B-grade watch. Layer 3: freshness filter Set a max listing age. My threshold is 72 hours for Rolex sport models, 7 days for vintage.…