I figure if you were building a £750 hipster shitster™, you'd probably be wanting to spend at least £50 on bits you could buy from Parker anyway and you might as well use them because they have very competitive prices and lots of stuff.
At the risk of this all getting pedantic and silly, those prices are for mountain bike tubes. And you have to add delivery. Unless you want to buy £50 worth of mountain bike tubes, in which case delivery is free. Of course, you've then got 20 tubes that you can't use in your 700c wheels.
I wouldn't call it pedantic and silly, just wrong ;)
http://www.parker-international.co.uk/4439/Continental-Race-28-Innertube.html
I figure if you were building a £750 hipster shitster™, you'd probably be wanting to spend at least £50 on bits you could buy from Parker anyway and you might as well use them because they have very competitive prices and lots of stuff.