Originally Posted by Sy Reene

Just because you raised another value proposition that didn't really get discussed.

The whole premise of this thread and the OP's question, really boils down to asking what is gained by paying more for a higher level groupset? High-level dimensions offhand I'd suggest as:
1) Weight
2) Performance (eg. Smoother, faster, more precise, etc)
3) Reliability (Finicky?, hi/lo maintenance)
4) Durability (parts longevity/service life)
5) Robustness (ability to sustain damage)

The problem is that aside from #1, which is the only easily measurable dimension, and possibly (eg chains) #4, the rest tend to be very anecdotal. Waiting on controlled sledgehammer testing to settle #5.