The problem isn't the developer building inefficient code on a fast machine, the problem is that you haven't defined performance metrics that must be measured against.

There should be defined, as part of the product requirements, a specific target that can be measured on all computers based off of the required customer experience. There are many websites (Check SpecInt) that allow you to relate your computer to other types of computers.

This is good for many reasons. It allows you to define minimum supported hardware more easily so you can limit the number of customer complains - we all know most software runs on most computers, it's just a matter of performance - if we set our specs so that people in the minimum requirements range has reasonably acceptable performance, you limit customer complaints - and then when a customer calls in, you can use the benchmarks to determine if there really is an issue, or if the customer is just not happy with how the product is supposed to work.