the price of genome sequencing is no longer dropping exponentially. And when it was, it was heavily amortized across very expensive machines that masked the true costs.
Let's just say that every analysis of sequencing costs I've seen has to play extensive trickery with the various costs (the capital cost of acquiring the machine, the operational costs of the reagents, the costs associated with staff running the machine, the servers required to store the data after it's acquired). Basically the stated prices are "the operational costs for a reagent" with the cost of the machine subsidized out or amortized or otherwise hidden from the calculation.
Many of the predictions about exponential genomics were done during a period of a few years where those misleading rates were published. I spent a bunch of time trying to figure out how to engineer systems to deal with exabytes of genomics data, but there is no reason to do that, because there isn't that much data being produced/retained or that needs to be maintained on spinning platters of rust. Just another example of bio hype, unfortunately.
