I'm looking for things like "in which decade does a program requiring X MIPS become cheaper than minimum wage?"

In about a decade we will have machines that cost less than $10,000 and can run roughly brain sized ANNs. However, this prediction relies more on software simulation improvement rather than hardware.

"when can 100 petabytes be stuffed into ~1500 cm^3 or less, and how much will it cost?".

Storage is much less of an issue for brain sims because synaptic connections are extremely compressible using a variety of techniques. Indeed current ANNs already take advantage of this to a degree. Also, using typical combinations of model and data parallelism a population of AIs can share most of their synaptic connections.