Things like x-factor, are relatively cheap to make, but more importantly they make shed loads from all the phone votes. They also draw massive audiences so the advert pay back is good.
So many of the TV drama shows will fail due to lack of audience means lack of advertising revenue. The American system of putting shows on a mid season break must also be very damaging as audiences often don't come back for the second part of the series having forgotten about it. One also has to consider the internet effect whereby a proportion of a potential audience don't even get the adverts as they have acquired the programme by dodgy means so the non originating TV countries don't pay as much for the rights to show as their audience has gone. the iplayer effect simply compounds that as I don't see how many of the TV companies are making any revenue from that.