I hear you, I just think that assuming that paying more gets you better quality is what keeps the brand name prices high.I'm sure there are good cheap options out there if you had lots of time to trial and error them all... the shortcut to this is paying more for a brand.
There are no guarantees, but fortunately I have time to do homework (and find it interesting), and think you can save a *lot* if you're smart.
The tapware and sanitaryware that I selected for our new home was $16K from Reece. I bought nearly identical stuff - though I upgraded the Reece standard bath to a spa from my eBay Australian-based hand-made custom bath manufacturer - from a couple of carefully selected Australian-based sellers on eBay for just under $7K. And my plumber and builder are both planning to recommend those suppliers to future customers.
Take out the bath and the comparison is $13K vs $4K. (The bath was $3K from either.)
I think $9K is worth saving!
But if you're not sure, I agree that saving $50 or $100 is probably not worthwhile, provided you're confident that what you're paying extra for is actually good quality, or has a better warranty or back-up or whatever, that gives you peace of mind.
Just paying more based on the assumption that paying more guarantees you better quality is, in my mind, pointless.