I see items like valves as one of those bits of kit that should be fit and forget but get a bad one and it will become a serious pain in the arse, often winding you up and almost certain to fail completely at the worse possible moment.
£12 for a product that is from a company that specializes in running tubeless, so probably/hopefully made to a high spec with good materials as opposed to £6 from a company that specializes in making products as cheaply as possible seems reasonable to me.
I spend hundreds on my wheelsets and tyres are around £30 to £50 a pop, no flipping way I am skimping on the details!
For the record i use Stans valves and run 5 sets of tubeless wheels, they work great. Not that I throw cash at stuff for the sake of it. I have used Gorilla tape on all my wheels as it simply does the job better than anything else, is lighter and just so happens to be cheaper.
Stoner – I lost my syringe years ago so use the same method as you but I have removed the cores a couple of times over the years when having trouble getting a tyre seated for the first time, normally on other peoples bikes, and it does help.