One possible reason for this discrepancy is that retailers such as Amazon and Best Buy typically have higher overhead costs than smaller sellers on eBay. This could lead to the same product costing more on Amazon or Best Buy, even if it is being sold by the same manufacturer. Additionally, eBay may have more competition among sellers, which could drive prices down.
Another possibility is that the sellers on eBay are selling used or refurbished products, while the retailers on Amazon and Best Buy are selling new products. This could explain why the eBay prices are lower, as used products are typically cheaper than new products.
If you're interested in purchasing an eero on eBay, be sure to do your research to make sure you're getting a good deal. Check the seller's feedback score, read the item description carefully, and contact the seller with any questions you have before making a purchase.