The cheap revolution is a first-order effect of Moore's Law. (Moore's Law predicts the transistordensity on silicon chips will double every 18 to 24 months.) For years if you said "Moore's Law, " people presumed you were describing a future of ever more powerful computers.
Since then, Li-ion batteries have barely tripled their volumetric energy density, while processor transistor count has zoomed more than a thousand-fold.