I'm in an awkward situation as I do not have two brushes of a similar nature at opposite ends of the price spectrum to offer a constructive view. I have two custom made badgers (Cadman) that are exquisite. I have three budget boar brushes (Wilkinson Sword and Omega) that are worlds apart with the Omega being more than twice the brush that is the Wilky, and two 'budget' synthetics (RazoRock Monster and Body Shop) that I liken in the same way as the boars, whilst both budget, one blows the other away.
The only logical difference that SHOULD apply is performance. Beauty is always subjective, but how the knot serves is the thing I care about above all. The thin and weedy knots on the Wilkinson Sword, whilst functional, are not a pleasure to use. Same deal with the Body Shop synthetic brush. They are too springy and fling lather around the bathroom in a manner akin to a Chimpanzee's tea-party would be.
I feel that with my Cadman brushes, I got EVERYTHING I wanted. Performance and aesthetics that appeal to me. Sure, they cost a lot more than all of my other brushes combined, but they give me pleasure beyond their function. They look fantastic and were built my a man who gives a damn about his craft, and that to me is what makes my pair of Cadman brushes much more valuable than my production run made brushes.