PicOne: "If you ever think 'for $1,500 I demand perfection,' this is not the article for you, it will just get you upset. The laws of physics are not suspended, nor are techniques of manufacturing altered, just because you demand it be so."
Perhaps not... but for the more money spent, the more I would at least presume the QC procedures prevent crappola from actually hitting the retailer shelves. Your term "allowable tolerance" I would also presume is a floating definition. Again I would presume that more expensive lens productions lines have more stringent definitions of 'allowable' applied.
Indeed you seem to argue the opposite, in that the potential tolerances are much greater with lenses with more elements/groupings (ie. more expensive lenses) than lenses of simpler construction, and that therefore buyers should expect more expensive lenses to perform worse than cheaper lenses.
I made the switch from SLR to DSLR in 2003 having started with 35mm in 1972. I've been shooting digital via Canon exclusively starting with a rebel, then 30D and now two 40D's and 5D Mk 1. With EF, EF-S and L lenses I have not once thought I had a 'bad copy'. Every bit of softness in photos of varied types (landscape, portrait, macro) was proven to be operator error. This great article confirms what I've always suspected - bad copies are rare but less that great combo's occur and user error occurs even more. But that's just my opinion (I'm an engineer in a disipline far from optics)
Yes, rule of thirds, golden mean, fibonacci curve or spiral - many names, actually many concepts of achieving a balance pleasing to the human mind. The RoT is the simplest portrayal of asymmetric projection and it goes on from there to severely complicated. on occasion a more involved perception of composition is necessary to set the artists mind in place. Some need a grid, some use the 'rules' without knowing they exist...