The Steep part is relative... There's a few guides that'll get you as close as the dyno tune without much fanfare if you aren't goign crazy with mods! Just my $.02

I would invest in HPT, because when you are done with it, you can recoup some of what you spent, but with the dyno tune, once it's done, the cash is gone and all you have is the tune, you can't even change anything if needed.