I Built a Cross-Platform Price Comparison Tool for Retail Arbitrage

Retail arbitrage is conceptually simple: buy a product on one platform where it's cheap, sell it on another where it's expensive, and pocket the difference. In practice, it's death by browser tabs. You're looking at a product on Amazon Japan. Is it cheaper on Mercari? What about Yahoo Auctions? You open three more tabs, type the product name into each search bar, scroll through results, mentally calculate fees, and try to remember the original price while comparing. By the time you finish, you've spent ten minutes on a single product and your browser has 47 tabs open. I went through this cycle hundreds of times before I decided to automate it. The result is Arbitra -- a Chrome extension that sits in the browser's side panel and compares prices across Amazon, Mercari, and Yahoo Auctions in real time. When you visit a product page on any of these platforms, Arbitra scrapes the product data, searches the other two platforms, and shows you a profit score telling you whether the arbitrage o