Tina it's actually a good question....
I think (and of course it's only a guess) that what you see in the first 'set' is the approach of color=set. Meaning that the artist sees ALL the various shades of turquoise for example as related - dark turq, light turq tranparent turq, opaque turq. Along this mindset, turq frit and casing with trans turq are all part of the color family in use and would (based on this approach) be part of the set.....
So my thought is that while all the turqs used in that first set vary a great deal visually and have very different reflection/refraction qualities (which is another aspect of lampwork beads that is very dynamic in the perception and appearance of color & artistic taste, (yet not one commonly considered) they are very 'technically' all of the same core colors used - turq and red.
Another thing that (can) detract from the visual 'matching factor' (IMHO) in certain colors/kinds of transparent glass is the fact that unlike their companions in the set your eye senses two other variables.
1) the reflection/refraction dynamics, (which alters the color compared to the opaque and embellished beads), 2) the visual difference - (sometimes even causing a slight deadening of the color) caused by the bead release that is quasi-visible in the interior of the 'clear' beads... So again, the spacer colors may seem even less of a match to what would appear to be the artists vison of the core color of the set.
Price is such a volatile variable - I've read, listened, watched and lived so many permutations of explanation vs reality vs marketing vs trend vs who can say? that I won't even wade into the riptide of market/price. One of my pet passions is marketing, yet I confess the reason it fascinates me is that it's so complex, layered and tied to personal (both seller and buyer) psychology and emotion. It's actually fascinating I think to see the range of responses to demand/desire from lampwork sellers and lampwork buyers mixed amongst economy, and endless assorted (and interesting!) variables.
Per normal I'm rattling on too long, lol... FWIW, just another insight into what may be the thought process behind the words 'lampwork bead set'.
Faith