Developer Builds Catawiki Deal Finder Using Expert Estimates Embedded in Page JSON

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A developer discovered that Catawiki, an online auction platform, embeds expert-estimated value ranges for every lot directly in its page JSON via Next.js's __NEXT_DATA__ structure. By comparing current bids against these expert estimates across a category, the developer built a bot to identify undervalued lots still open for bidding. An initial plan to analyze completed auction price history was abandoned after finding that Catawiki's public search only surfaces live lots, with no accessible archive of closed sales. The tool was reoriented into a live deal finder, with a key filter being lots closing within 24 hours that are still priced significantly below the expert estimate. The bot has been packaged as an Apify Actor, allowing users or AI agents to query deals by category, time window, and minimum discount percentage.

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