Don't let your engineering degree stand in the way of finding out the facts. You claimed a 2 kW vacuum cleaner would clean in half the time, and there's plenty of data that suggests otherwise.

The claim that cleaning time is linear to motor effect is unrealistic at best. There is an optimum effect for the nozzle. A 10 kW engine wouldn't clear your floors any faster than a 1 kW one, and definitively not ten times faster. The best (household, not for garages or anything like that) vacuum cleaner commercially available on the market is likely closer to 1 kW than 2 kW.

You think only "average" people falls for marketing tricks, but this superficial knowledge of the engineering involved actually makes you an easier prey for the marketing trick that more powerful motors makes for a better product. That bigger numbers are better is one of the easiest marketing schemes ever.