Sirobo
I think that you may be asking too broad a question.
I am based near to Alton Towers - Staffordshire and have been fortunate to have had a reasonable amount of success in both window cleaning and commercial cleaning (external - hard cleaning) and this is ongoing.
I have had contract work - window cleaning that has paid me more than I could have earned in a month (in my previous job), for one days work. I would see this as very much not the norm.
I also had McDonalds on three weekly cleans @ £18.00 per clean. I had pubs between £20.00 to £40.00, nursing homes between £40.00 and £60.00 but I had lots and lots and lots plus lots and lots of domestics on a very tight round.
How did I price, I tried to find out what they were charging, I would ask them outright!!!. I would try and work out how long it would take me to clean at my domestic hourly rate.
I would then charge an hourly rate plus travelling and or adding £10.00, £20.00, 30.00 to the price.
When you have a full work schedule it is easier to charge what you want because if you don't get it it doesnt affect you.
It isn't as easy as to ask for a price because the variables are many and you may have more need than me to get the job so you will price it cheaply to get it.
I have had 9 years of pricing and can gauge quite quickly how long it will take and what I shouuld be charging but I can still get it wrong.
Rob