If somebody can make a rational argument about why the Rivendells are better in a rational/practical way (probably easy to do) or why that advantage is worth the cost, I'd be interested in hearing it.

The difference between a Riv frame and, just for comparisons sake, an LHT, is the same difference between a Chevy and an Acura—materials, craftsmanship and styling. Pretty simple.

Note that an Acura costs more than a Chevy of the same type.

I forgot to add engineering (not so big a point here) and number of units produced.