$20-$30 per night is absolutely ridiculous! If you stay in a suite at a 5* hotel, housekeeping will typically spend 30-60min cleaning the room.
They obviously donīt earn a fortune, so tipping a few dollars goes a long way and usually is appreciated...
I usually tip $3-$5/night, very rarely $10 if I have a very large (1000sq.ft.+) suite, made a big mess and have some special requests, but thatīs definitely the exception. I usually leave a thank you note and some change (as I hate carrying around coins anyway).