I am actually healed from cheap floor cleaning robots, but I4U Reader Dario O. tipped us about the Robo Maxx sold also in Germany. German Amazon sells this floor cleaning robot for only 49,00 Euros (~$60).

The Robo Maxx actually seems to be a vacuum, not just a brushing machine.
Update: I4U Reader Gabor B. tells us that it has no vacuum function.
User reviews vary. Some complain that the dust container is full too fast. Well that actually would mean it cleans. The Tchibo robot we reviewed had issues with that. Overall it is more a toy than a real help cleaning.
The upcoming iRobot Scooba is promising, albeit it will sell for $399.99 and not just for $60 bucks.