Is this a hotel or something similar? You'd probably have to consider HOW you're going to do the job first, before you work out how much.
> Can they afford much down-time? If not, extraction is out - dry or LM cleaning are going to be your choices, which can limit the results.
> Are the cushions fixed on the sofas or removable?
> Is it going to have to be done overnight? Do you want to work at the same rate for night shift as your daytime rates?
> Are you planning to do this on your own? Surely there's a good few days' solo work there, they might not want the job to drag out that long so you may need a helper or two. That means they'll want paying!
> They're very high curtains. Possibly too high for even a step ladder, but it's difficult to tell from the photos (shut the curtains to take a photo next time!!). You'd probably be on the wrong side of H&S laws unless you got a tower scaffold in to do them. That costs you money and takes up more time.
There's probably loads more stuff to consider, but these are the first things that pop into my head.