WHAT A QUSTION... how much is your time worth? ... are your cleaners vetted and trained... do you provide a proffessional, reliable, trustworthy and flexible service? Are you properly equiped and insured, a member of a professional body perhaps?
The better the service the higher you can charge .. check out the competion what service do they provide for the money..
We deal mainly with commercial clients, the few domestic clients we have are with us mostly by recommendation from our commercial side, it is a lucrative but troublesome market. We are not cheap but we do an excellent service.. I don't have the time to thoroughly check out enough of our cleaners to put into peoples homes .. they need to be more trustworthy than me .. my reputation is at stake, so £5-£6 an hour would be a joke for staff of this calibre. You have holidays etc to consider. I turn domestic cleaning away all the time, I find that all to often people expect a high service at a cheap price, but if I focussed on it I would be looking for a handsome return.
So all in all profit margin can be higher if you cut corners but comfortable if you don't.
Good luck.