[badpun]

They could be shared, and work practically non-stop (minus nights, as that would wake people up). That'd bring the per-consumer cost down by a large fraction. The sharing would likely be organized by a commercial third-party, but still, it could be much cheaper than human cleaners.

Having said that, it could still be decades till the robot is ready to be released into human homes unsupervised. The variation in human homes, what people store in them etc. is not easy. However, it could be ready for hotels much sooner.