The Valorstones/Crests search will do a ranking based on cost efficiency. Start by reading the description in this post:
I have not looked at how raidbots does the currency search, but that post should explain some of the reasoning behind our approach.
Something worth mentioning that is not in that post: how much of each currency you have right now is usually not that interesting which is why we don’t use it. Of more interest is how much of each currency you are willing to spend time getting – usually you will get some of each currency every week.
That is another reason why we arrived at a system that tries to equate your currencies to effort/time and use that as the “unit” for an efficiency ranking, rather than simply looking at how many of each you currently own.