Firstly, let me say I was an existing TalkTalk customer, so can only explain from that perspective.
As a TT customer, I pay £14.50 pcm for telephone line rental, and £14.50 pcm for my broadband service.
The YouView box was subject to a £50 installation fee; but this also included a brand new router (which is now also my WiFi-provider for this laptop I am using).
The £50 was added onto this months telephone bill.........and that is it, as far as finances go! :o)
The box itself is surprisingly small (12"x8"x2"). It is connected to the router (and therefore the router needs to be plugged into a telephone point) and needs a connection to a roof-aerial, too.
Now it is possible for me to tape two-channels at once, pause live-tv (if the 'phone rings half way through something), scroll-back to the start of a programme (if I didn't have chance to pause it).....go back up to 7 days to watch something. It records programmes without the need to build in 'buffer-times' before and after the broadcast times. Recording is done by highlighting the programme in the on-screen guide-list and pressing a single button!! This same button allows you to record an entire series without the need to reset every week. It allows access to all the 'players'; ITV, BBC, 4onDemand, etc., where there are entire back-catalogues of series to watch (I'm presently working my way through Misfits).
I'm completely besotted with it and am rather looking forwards to the cold, dark nights and rotten winter-weather as I shall then have a good reason to stay in with my YouView box! :o)