@Mark,
While there is some truth to what you are saying, I believe it is not always as straight forward.
Programmers and people in general don't always take the time to evaluate all the possibilities and decide to switch languages. Often It's the managers that decide, or the schools that teach the first languages ... and programmers never have the need to invest enough amount of time to get to a certain level were they can decide this language saves me more time than that language.
Plus you have to admit that languages that have the backing of huge commercial entities such as Microsoft or Sun will always have an advantage in the market compared to languages without such backing.
In order to answer the original question, Paul Graham tries to give an example here even though I admit it is not necessarily as practical as I would like :-)
