Backblaze posts some good stuff on HD pricing and reliability. Here's a good chart from their data: https://www.backblaze.com/blog/hard-drive-cost-per-gigabyte

Backblaze posts some good stuff on HD pricing and reliability. Here's a good chart from their data: https://www.backblaze.com/blog/hard-drive-cost-per-gigabyte/ https://www.backblaze.com/blog/hard-drive-cost-per-gigabyte/ They also link to this great (logarithmic) chart: http://www.mkomo.com/cost-per-gigabyte-update http://www.mkomo.com/cost-per-gigabyte-update TL;DR: price hasn't been dropping by half annually, but prices have come down from ~$0.70/GB to < $0.03/GB now. So roughly a factor of 20 over 13-14 years, somewhere in the neighborhood of 25% improvements compounded annually over that time.