Yev from Backblaze here -> Some of the responses down below are correct - it really does come down to price. We run a fairly lean ship and so the price per gigabyte is weighed pretty heavily when we make our purchasing decisions. We have a post where we go into the cost of hard drives over time, it's about 3 years old now, but still a good read -> https://www.backblaze.com/blog/hard-drive-cost-per-gigabyte/.