I guess it all comes down to personal preference.
I paid ~$1500 all up for my exhaust system. The extractors were $440, with $250 HPC plus another ~$250 for postage and labour. The other $500 went into the high flow cat and cannon.
When I did it I thought "great, an extra 20rwkw (plus the low end power) on my NA Supra is just what I need", spent all the money and was... unimpressed. I don't want people to make the same mistake. It's definitely there, and you can feel it, but its nothing amazing.