There isn't really such a thing as a decent cheapie - cheapies tend not to be ultrasonic at all, just high frequency vibration. And a cheapie that actually IS ultrasonic will wake the dead with the noise.- though you can quiet them down a bit with some of that draft excluder stuff round the lid to stop it howling. A decent cheapie would be like an ice cream van that came round in the evening, drove to the middle of an industrial estate somewhere, turned his machine on and legged it for half an hour, then dropped your stuff back. New service, maybe?