In our area there will be customers who expect a day's work for £100. There will also be some who expect to pay £200 (probably more people in this group than the first group). There'd be fewer who expect to pay £300 and there'll be some who are happy to pay £400+. In different areas the numbers may be different: Kensington higher, Livingston lower.
The same goes for the price of a clean of a standard house, if we're discussing that rather than a day rate.
Basic economics says that there will be suppliers at each of those levels. If you doubt the lower numbers, imagine someone on the dole who's offered £50 cash for a day's work. He'll probably take it.
So, as far as I'm concerned, it's your choice which market you go for. I'm not suggesting you should go for the £400 customers, as they will be tougher to gain and retain (you'll need to offer a good service - not just get their windows clean) than the £200 people, just that it's up to you which market you go for.
And it's not a matter of "getting away with" anything. If someone's happy to pay a price (whatever that might be), they'll be happy customers. Very happy.
So, go for whatever day rate you want and don't care about what other people are doing.
Vin