thegman: First of all, my decision to buy an Iyonix was nothing to do with the maximum amount of RAM I could put in a Risc PC. (I never expanded my Risc PC beyond 192MB, although I have to admit 512MB in the Iyonix is very nice to have).
Secondly, your numbers don't add up. The Risc PC example in the article is 490ukp. Just adding Select to that (150ukp for a new subscription?) would take the total way over the 600ukp you mention, even before looking at buying a ViewFinder, a 100Mbit network card, et cetera.
I've never heard of Pegasos (I presume it doesn't run RISC OS), but do remember that selling a motherboard and selling a complete system are very different things (you need to make sure ethernet and floppy drive work, for example )