I'd be interested to see something like this but rather than a straight cost comparison, an analysis of what it got you in the marketplace. If you had this kind of compute power in 1976, what could you do that your competitors could not, and what was the multiplier to the business. With computing ubiquitous now the hardware doesn't always provide you with a significant competitive advantage, but I can imagine in 1976 you could own an industry that way, and $300K may have seemed like a steal.

EDIT: The post might be something like: "Why we bought a DEC for 300K and never thought twice about it"