Upon further research I have a pretty good idea about the prices for xur's equipment. As far as weapons 23 strange coins, armor goes for 13 strange coins. For exotic engrams, 23 motes of light. Let's get on those weekly heroic strikes for those coins and we should get some motes of light from rare engrams. I did notice that there was a stock refresh, so there is a good chance the stock will change weekly, but at least we have a general idea of what things cost and might cost. He is currently by the speaker, having changed location, as he is available Friday - Sunday.