i would of thought if you are just looking for a cheap place to stay then a cheap hotel would be better as i imagine these places would make you have a massage for you to be able to sleep the night and cost wise for a 1 hour massage may be 100 rmb in smaller cities.

In Hong Kong airport I had a 12 hour layover and there were no hotel rooms, so I found one of these places you mention in the airport. It was aobut as expenssive as a hotel room but I was able to comfortabley kill time unitl 1 hour beofer my flight.

I have been to quite a few of the giant sauna spa joints in Shenyang. They are a number of stories tall, the biggest was 7 stories, with large spa pools, saunas, scrub areas, outside spa pools, buffet restaurants and individual or group massage rooms. I have even been to one that had about 100 reclining lounge chairs with their own video on demand screens where you could relax and have a massage. I was surprised  when a live magic act happened on a stage at the front of the room but was told that they always had some live performance every two or three hours on weekends. I have spent up to 6 hours in them and am sure you could just nod off in one of the recliners for as long as you want. In fact quite a few locals seemed to be doing just that.

I stayed in such a place in Nanjing.  I had forgotten my passport at home and couldn't check into a hotel.  A local found a massage place for me, much like how woody described it.  It was much cheaper than a hotel and I stayed in the lounge chair room with a big TV the whole night.  Pretty girls and massages were upstairs.