I honestly dont know..... (I assume it costs,otherwise they wouldnt care if people watched them in SD)
I only ask because I don't pay to watch HD TV. Virgin Media has unveiled a new set top box offering access to its high definition channel lineup without the need for an additional monthly fee. Launching on March 22 2010, the new HD receiver, named the V HD Box, will be open up access to the cable operator's HD channels at no further subscription cost for consumers. New and existing customers across all pay-TV tiers (M+, L, XL) will be able to 'purchase' the receiver for £49 plus a £35 installation fee, but then pay no monthly HD fee. The receiver, created by Virgin Media's partner Cisco, includes HDMI, SCART, USB and Ethernet ports, and is also geared to support 3D services. Looking into it, I do understand it did cost quite a lot extra once upon a time, a time when there was virtually no HD output...but - I suppose - they had to recoup the cost of the HD ready boxes and other associated costs of providing HD. I have also seen there were legal reasons for the cost too. I'm sure it is the same where you are too. Now everything seems to be in HD...and it's free. Whoop. I'm not quite sure if it (HD) is a scam or not, I imagine it is. I would not pay extra for HD, tbh. Btw, I'm not quite sure what you mean by watching HD in SD.
Well I hooked an HD converter box up to my STANDARD CRT TV and watched the HD stuff fine in STANDARD DEF.. (The cable company doesnt have to block the HD feeds from the standard boxs as the feeds i believe are made BIGGER by the BOX (OR tv if the cable is hooked directly in)))