Something i'd like to add is, it's not always about who's the cheapest.
One off my clients has told me i'm expensive, but i still get all his work, as the last thing letting agents want is poor quality cleans. We sell on quality, as alot of end of tenancy work is clean it one day new tenants move in the next, so as the agent goes over the check in the last thing he wants is when he opens the oven it's not been cleaned properly especially with the new tenants in tow.
Hope my example has been of help, some may disagree but that's my view
Arthur