am only guessing bob but i presume its as simple as £8.99 for 2 rooms.
pay what you like will get you in the door then its up to the techy to upsell while putting down the job for that price. but like i said i'm only guessing.
something like "oh you want to pay £40 for the whole house, well i can do that but i couldn't use any chems or wouldn't turn a profit, if you had the chems and by the way, heres the difference between the 2 cleans,it would only cost an extra £?? and then we could get that stain out for xx" and so on and so forth
i'm sure monty can explain it alot better seeing as its his or his bosses angle. looks like a franchise of sorts,
anyway, where does it say £75 for a 4 bedder?