Some users have been seeing these green suggestions when performing a search on the Play Store app for almost a year, but the feature began rolling out more widely in June (I still don't have it). However, it only seemed to provide keywords to further specify your search, not proper filters to separate the results according to price. Now it looks like Google is testing the latter kind.

Reader teh Jax is seeing "free" and "premium" filters among the options when he performs a search on the Play Store. Sometimes, they show up from the first go, like here:

Other times it takes a first step of narrowing down to get them to show up, like when looking for an MP3 player:

The behavior isn't super consistent though. As teh Jax pointed out, some searches don't show the "free" and "premium" filters at all, like in the cases below:

I'm also a little intrigued by the "top rated" and "no ads" filters that are showing up in some of these searches as well. As far as I recall, those weren't there previously either, but I could be mistaken.

These filters are so useful that it baffles me that Google has taken this long to add them, and they're still server-side enabled for only some users. Ugh. Goodness now Google, for a search company that knows exactly which results to surface, the Play Store searches are absolute garbage. Filters for free, premium, IAPs or not, ratings, download numbers, ads or not, and category should be mandatory to make the gazillion titles easy to parse through.