Dollar for dollar you are quite possibly correct. That set-up of Brents is exactly what I had, including the Koni bumpstops (Progress rear sway). Worked quite well, street and my one track excursion, if a bit harsh. Although on "harsh" keep in mind that I am an old fart, YMMV.
IIRC, around $440 for the AGX's on a GB, Hypercoils were 325'ish shipped, and the Koni bumps were 60'ish (?). OEM boots, new thrust washers, Superpro (Whiteline) caster bushings, yada, yada. It took me 18-months from the Hypercoils purchase, with them sitting on my steps in my house, until I had enough money to assemble the rest of the suspension and get it all installed.
Still glad I waited and did it the best I could afford at the time.
I will add that the CSK/Hyperco set-up, while certainly more pricey, is vastly superior. No question about it, far more comfortable, a bit better planted.