At the moment, only gems are shown in the merchant, although different items can be purchased with a number of "currencies" eg. star coins, beans, stalks, guild coins... possibly more, can't think of them off the top of my head
It would be useful to have all these currencies listed at the top, so we can see if we have enough for, say 2 of this and 1 of that without having to go and look in the mayor's house or wherever.