So you are in command of all the facts, genuine GM have a weld seal all the way round the vertical bush 'collar', aftermarkets (as mine are) tend to only have a few blobs. They have been known to fail, under extreme pressure/abuse, however 30k done on mine and no death yet
I'd say its very very very rare.
For this reason some people prefer to use second hand GM ones, clean up, repaint then rebush etc.
However, that ATP price sounds like the right sort of ballpark. They do (well, did at least) a kit of wishbones, droplinks, track rods for maybe £80, I seem to recall.
Consensus on here is if youre touching the suspension, do the lot, get a geometry set up at the same time. Don't have a geo setup, save £50, but burn through three times that in tyres per year before you realise your error... if you see what I mean.