The Kings / Roo Systems and a number of other brands are all made in the same factory in China. Basically, you get what you are paying for.
They're all OK - if you're looking for a cheap option that you only want to use for a couple of years or so before they fall apart.
Something like a Southern Cross Canvas like these 
Dome Swags - Southern Cross Canvas Products made in Australia from Australian canvas are a much better quality option, but at about double the price of the Chinese made stuff.
Very bulky and heavy though - actually takes up more room on the roofrack than an Oztent RV5.
And the requirement to seal them properly before use as described by DiscoMick applies equally to the more expensive ones as to the cheap ones.