Hi Matthew
The reason 'no one seems to know' is because each cleaning job has its own unique quirks (like how dirty is it, will there be people on-site who will hinder the operation, do you have to drive miles to collect keys, are there lots of stairs and stuff which will increase the time spent humping your equipment round the place? etc) and also your own quirks (like how fast do you work, will you be needing many tea/coffee/fAg breaks, what time you are at your peak? etc).
As has been said already (and its as good as it gets i'm afraid m8) you need to add up your costs, decide how much you want to make out of it, and decide what you think the client will pay.
If you have an indication of what they would have to pay one of your competitors then this will help. It may also be to your advantage if it is that they need the work doing soon (if of course you can do it in the timescale they require).
As for the 'emergancy' call out, you really need to get this spot-on and find out what they would have to pay another company to do it. Base your price on that. Its no good saying you will charge double your price as another company MAY do it for less, and at the same time its no good saying double as another company MAY charge more than your double. You dont want to outprice yourself or charge too little.
If the rooms have been deep-cleaned already you need to assertain what condition they may be in when they've been occupied and then vacated again.
Who is it that will be executing the 'emergancy work' ? Will they require more money? Will they be reliable? Etc.
Cheers
Stephen