You're right.
When you come to the point of working 12-14 hours a day, and you have an opportunity to spare let's say an hour thanks to a more powerful comp, cutting the time of the pure computing, then the answer is pretty clear.
Not to forget that as a pro you have to make costs.
sash
Nobody denies that but if your a PRO working 12-14 hours a day let's say in photoshop then 2% is not worth the $500 no matter how you look at it. Get RAM for that $500 and you'll see a big difference in this case.