Sticking with the thread title... the prices quoted are all about right, £330 ish... but if you search this forum on top box... general consensus seems to be that the box is overpriced, low quality and that you're better off buying an alternative top box....
not to mention the fact that there are NUMEROUS reports of the BMW box "falling off" yes.. thats right... Falling off....
your money... but i'd definately consider other options before spending your real world money !!
You can spend less, get better quality, better volume from something like a Givi E52, plus be able to put a couple of lids in it too when you stop .....
good luck choosing.....