I randomly decided to look at the Amazon listing for recertified 10TB HGST drives that I previously bought back when they were super cheap. I noticed that Amazon had two returned units (via Amazon Resale) in stock for only $57 each! I immediately ordered them since there's a 30-day return period, and they appear to be untouched and still have the tamper-proof seal. They also came with the 5-year warranty card, though I'm not sure if the recertifier will honor that since I bought it from Amazon Resale. They're sold by Worldwide Product Importer which I believe is affiliated with GoHardDrive as they sold them under the MDD brand.
They have zero bad sectors, and I'm running extended smart tests now to make sure they're actually in good condition, but I feel like I struck gold finding good-quality recerts for only $5.7/TB in this market. I just wish they had more than two in stock.