I spent around $1500 on an upgrade for a 2 month old Mac at one time. A year later stock machines were that fast and two tears later I upgraded to a faster machine again which I also upgraded shortly after buying it. It may not seem as worthwhile from here but I couldn't buy that fast a machine from Apple and if it didn't pay for itself in the time saved, it did make the machine a lot more enjoyable when you're pushing your hardware limits.