New Seagate Exos X20 20TB 7200RPM 3.5" HDD - $240.29 (with Promocode ZIP111)

They have some 10TB helium for roughly the same price/TB.

https://www.newegg.com/seagate-enterprise-capacity-3-5-st10000nm0016-10tb/p/N82E16822178941?Item=9SIA5ADK6G7340

https://www.newegg.com/seagate-exos-x10-st10000nm0126-10tb/p/1Z4-002P-022A9?Item=9SIA5ADK030931

I'm not sure what the difference is. They look like the same drive with a different model number. 3 x 10TB in RAID 5 -OR- 2 x 20TB in RAID 1? Decisions, decisions....