Change Default Instant-Search Sort Order

How do I change the default sort order on the instant search page?

It is always set to “Relevance” on initial load. But, I want the default selected option to be “Most expensive first”.

I have looked at this previous post BUT… it does NOT change the default selected option. The solution posted simply reorders the sort options (see image below)


As you see, “Relevance” is still selected by default.

So, what do I need to modify in order to get the default sort order to be “Most expensive first”.