I know these are going to be a bit pricey, but there are 8x 128GB 2400MHz LRDIMMs for $6K and 2666MHz for $8K on ebay. These are under $600 ea so under $4700 for 1TB of RAM and the seller has a bunch. That's not too much of a premium for big capacity dimms.
Hynix 128gb Pc4-2666v 2s4rx4 21300 ECC LRDIMM Server Memory Hmabagl7a4r4n-vn for sale online | eBay
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