I got mine dirt cheap, for £95 from a shop keeper I know.
I weigh 65kg and figured that as he only had two in stock, a child pair and an adult pair, that he was probable to have picked a mid-weight adult/child. And with the lower bracket of bocks being for 60kg and upward. I think probability favoured me that these were likely to be of a good enough weight for me.
Any way I can know for sure though?
If it helps ^