That's including the enterprise premium for software, hardware support, and licenses. Building this in-house using open source software (e.g. Ceph) on OEM hardware will be cheaper by an order of magnitude.
You of course need people to maintain it -- the $300k turnkey solution might be the better option depending on current staff.
Priced out by whom? What kind of object storage? Were you looking at the price of drives, or the price of a complete solution delivered by some company?
or outright buying hardware capable of storing 850TB for the same $20K one time payment. Gives you some perspective on how overpriced AWS is.