The Tau 'Cello spike is made from extruded aluminium, black chrome plated steel and stainless steel parts. It is reasonably tough and should not break in normal use (we've never had one fail yet) though it's certain that given enough abuse it would fail. When maximally extended it's a long lever, and you will break it in some way if you whack it against a hard surface, sideways on, with enough vigour. We haven't seen this as yet, but I'm sure someone will have a good go at some point. It will not fail in normal use, you will need to do something nasty to break it.
It's expensive for several reasons - firstly it's way more complicated that you'd think as it had to meet a very specific (low) weight so that it didn't ruin the mass balance of the Tau when it's attached, which means that it can be left on when using a strap. This was a serious design challenge (it took our head designer months of work) and to meet it required a lot of engineering effort and testing. The end product, like many 'designed to be light' objects doesn't feel like it's worth £200 and we have had people say things like 'there doesn't seem to be much to it for that money', which does kind of miss the point as the 'not much to it' bit is exactly why it costs quite so much. We also make them in small quantities and they involve both bespoke extrusions and a lot of CNC machining. These processes only become cheap in very large quantities. For your information, we make very little selling you one as the parts alone come to more than £100 to have made. I originally wanted to ship one with every Tau, bit this cost sadly prevented that being an option.
I hope that answers your questions.
John