There's no reason to expect the price of a two-platter hard drive to go down over time, and hard drive tech has not quite improved enough to allow for 2TB from

There's no reason to expect the price of a two-platter hard drive to go down over time, and hard drive tech has not quite improved enough to allow for 2TB from a single platter without using shingled magnetic recording. Drives with at least 1TB per platter appear to have been on the market since just after the floods (2011/2012).