In general you tend to get what you pay for. the more expensive kits are a better quality than the cheaper ones. this is not to say that the cheap ones are not very good. My first kit was a "Youngs Harvest Stout". I bought all the equipment and brewed as per instructions. 8 weeks later, i was gobsmacked, what a excellent beer. i then progressed up to a Wherry, then to a top of the range kit. they were all very good.
Is a expensive kit twice, sometimes three times, as good as a cheap one? ...no
but you can taste the difference