Re: Officially no series 8 in 2013
I wouldn't go quite that far, but Game of Thrones, with its enormous scope, certainly has a much larger budget requirement so the 10 episode seasons can be justified because of the cost to do any more. Because of the nature of the show they can't get away with a couple of sets on a sound stage for some inexpensive filler episodes like Doctor Who often can. Has nothing to do with how much work goes into it though.
More accurate to say that Doctor Who is a comparatively inexpensive series to produce, with a comparatively easier schedule for the cast and crew. That seems to be true in general for BBC productions though. American productions are insanely grueling at times in the name of getting the best bang out of those much higher budgets.
Remember DW has a regular cast of 2-3, who are in the majorit of the scenes, when you have a cast of 7. You can spread screen time around more. So you can be filming two differenct scenes you two groups of actors at once. If your principals are in almost every seen you can't do that.
On the continent of wild endeavour in the mountains of solace and solitude there stood the citadel of the time lords, the oldest and most mighty race in the universe looking down on the galaxies below sworn never to interfere only to watch.