Re: Bewildered. (That's grown-up speak for "wtf")
"The cheaper models will almost certainly be less power and water efficient, noisier, probably slower, and possibly a bit more crap at actually cleaning"
Generally I'd say no, they aren't. Noisier is very likely but is absolutely relative to the installation, since most come with fairly decent sound proofing and room for improvement. Mostly, the cheaper ones are the stock from last year, the year before, the year before that, and the year before THAT.
<An associate had to do some cabling in a whirlpool warehouse ..... and learned many interesting lessons about large appliances that day.>