The main component of this is a second-hand marketplace – something like the part of Craigslist that lets you sell your second-hand items. People list second-hand items for sale.
Users can search the site to find items, but the primary mode of discovery is via the browser plugin which will detect which item they are looking at on Amazon or similar shopping sites and show them comparable items available on the marketplace, along with the savings. It would prefer showing identical matches, but could also show similar items either as a secondary option or the only option if no perfect matches are available.
Shown items would either be items the seller is willing to ship to the buyer’s location or that are in the user’s area.rrrru