Sound and Vision lists their prices here:
http://www.soundandvisionmag.com/article/kef-rolls-out-r-series
I wonder why the surrounds are so high priced? Sure, they have 2 drivers each, but that is kinda a waste of cash to pay that much for dipoles, IMO. They do very little work compared to the center channel, and those are priced at $1499 or $999. I doubt I would ever put together a system where the dipoles cost more than the center channel. This seems to be trend among manufacturers. If you are on a budget you can really save by getting cheaper surrounds. You would probably only notice the difference with 5.1 music, and for that people recommend using regular speakers for surrounds, not dipoles.
Still, overall the line looks quite nice.
I wonder why you wonder why the dipoles cost so much, since you recognize the fact that you are buying a whole lot of drivers with a pair of dipole speakers. With one center channel speaker, you have one of the Uni-Q driver arrays, but with a pair of dipole surrounds, there are four of them, so that part of them should cost four times as much. Granted, the dipoles don't have the lower woofers, but we can get an idea of their value by comparing the R100 with the R300, with a price difference of $600 for having a pair of the 6.5" lower woofers. The R100 is a bookshelf with just the Uni-Q driver array, and it costs $1200, compared with the $1800 for the dipoles, which is twice as many actual drivers at only 50% higher price.
Comparing these (the aforementioned R100 with the dipoles), since the added drivers in the dipoles add $600, we may (for the sake of simplicity, not absolute precision) regard the Uni-Q array as $300 each, so the dipole should be $900 more than the one center channel speaker, except that we need to add in that $600 to the center channel price for the lower bass speakers (see comparison above of R100 and R300), which means that the dipole speakers ought to cost $300 more than the center channel speaker with the two 6.5" lower woofers. And that is precisely how much more they do cost than the R600c center channel speaker.
There is, however, one small matter relevant to the above calculation, and that is that the Uni-Q driver array is larger in the dipoles than in the other speakers, and so they ought to cost even more than they do. So KEF is really selling them at a discounted price relative to the other speakers.
If you don't want dipole surround speakers, you could go with the R100 for $1200/pair instead, to save $600 off the dipole price.
I personally expect to pay more for the surround speakers than for the one center channel speaker, but I use identical speakers in all channels (which is the only way to have truly perfect voice matching), so each speaker costs exactly the same as any other speaker (excluding subwoofers, of course). If I were going to go with these KEF speakers for a surround system, I would probably get R100 for all channels (depending on how deep, exactly, they go), and then spend the savings on multiple better subwoofers, to get better bass than one would otherwise get for the same amount of money.
In any case, dipoles cost more to buy because they cost more to make than comparable monopoles. This should not be a mystery to anyone.