Your e-shop data lives in three places that don't talk to each other

I recently scoped a project for an e-commerce client running PrestaShop. Smart guy, profitable business, good product margins. He had one question he couldn't answer: which of his Google Ads campaigns actually make money? Not which ones get clicks. Not which ones drive traffic. Which ones drive purchases of products with margins high enough to justify the ad spend? He'd been running Google Ads for years and couldn't tell me. The data existed. All of it. Sales data in PrestaShop's MySQL database. Ad spend in Google Ads. Traffic patterns in Google Analytics. Three systems, three dashboards, zero connection between them. To answer even a basic cross-channel question, he'd have to pull a CSV from each, line them up in a spreadsheet, and hope the dates and product names matched. He didn't do this. Nobody does this. So the money question stayed unanswered. This isn't a PrestaShop problem. Shopify, WooCommerce, Magento — doesn't matter. If you sell online and advertise on Google, you almost c