My personal experience is that the cheap ones only last a short time, ive had i think 3 nilfisks's great when they work...I bit the bullet about 5 years ago and bought a Kranzle K7 - worth every penny and last longer than the cheap ones, I had an issue recently and I had it it repaired quite cheaply where as the nilfisks just got binned and not worth repairing.
That's fair enough and I certainly understand that thinking. I guess though with limited cash/not that high on my priority list then given my last nilfisk cost 50 quid or so and lasted around five or six years I see it as a disposable item. if my new karcher lasts two years for 44.49 then I'll be happy.