Remember, if you hire someone without a company, that person is your employee and (if you exceed the nanny tax threshold) you'll need to pay taxes, do withholding, check that the person is legal to work, etc. That's a big part of why I use a company - so that that's all their burden, not mine.
That said, the quotes you're getting do seem high - I'm paying about that for a SFH that's about 1000 square feet larger. Try a smaller company rather than the Merry Maids type operations. Check Washington Consumer Checkbook (you can get it at the library if you don't want to subscribe).