Basic question really, do they help much with kickboxing?
I know they are fairly cheap but is it worth getting a set?

Yes, it is.

The support itself isn't anything revolutionary, you can still twist your ankle if you're not careful. But it does help alot because while you work you're at least 80% of the time on your toes and it helps releave the pressure from your tendons and ligaments.

The biggest gain is when you are kicking thai pads or a heavy bag. Wearing ankle support will drastically reduce the redness of the skin and possible cuts on your feet.

You don't have to buy original thai support from pride or something, you can buy the basic ones from a drug store. I use these all my life (for about 3 and something years now ) and they are just fine.

To summarize, yes they have a purpose besides being all fancy and stuff.

that is actually nice to know, i have screwed up both of my ankles over the years from various dumb bmx fuck ups.