To start off, everybody does it is a appeal to popularity, a logic fallacy. The number of people have no bearing on how correct or incorrect something is. Just today I saw a speeding car was jammed under the trailer rear of a big rig. Both the driver and passenger dead, causing the highway to be completely closed and long traffic jams, do you approve of their speeding because everyone does it?
I am not a track guy and could care less about track numbers as its nothing more than a dick and wallet measuring contest to me. Its not anyones idea of a good time, just yours as the only mind you can read is your own, and I didn't spend anyware near 5k on my emission legal build. I spent more fixing GM shortcuts in my Regal's body than anything else.
I never said the suspension problems can't be solved, but its expensive and labor intensive which is a turnoff considering you can buy newer used cars that handle far better stock. Its not just tall ball joints but also redesigned arms that take advantage of tall ball joints. Plus your stated price quote is missing a zero. Any improvements in making the suspension stiffer simply makes the floppy frame and body flex more, requiring bracing and reinforcing. Tall ball joints and arms are just a drop in the bucket.
G body suspensions are setup for comfort and easy correction for stupid moves by drivers. So if you do something stupid, it easy to correct, but it is also easy to exceed the suspension's capabilitles. The old muscle cars do not correct so easily but are easier to improve upon at a lower costs to better results and more difficult to exceed their capabilitles.
All G body Regals except for GNXs, have the weakest body setup from the factory. Missing body bushings, lacking most of the bracing, poor roof welds, it was a sick joke by GM. Its why many turbo Buicks have distored bodies. Just 110 hp from my old 231 cracked the roof on my Regal. Had to perform a lot of work from replacing body bushings and installing missing ones. Welded in a rear seat brace and better welded the roof seam, which are poorly fitted and welded by the factory. Huge gaps just covered with filler, rookie mistakes by GM. Also added a GP front frame brace.