Well, even if money does matter, the tradeoff is often more complex than just the one-time hardware cost. If you are a software engineer whose time is expensive, and a slower workstation processor means you wait an extra 5 seconds for a compilation 100 times a day, then the time costs add up quickly.
I would imagine the same is true for e.g. server response latency when that latency correlates to user experience and thus growth/popularity of your service. People might not notice a few ms, but 100ms vs 300ms is definitely visible.
