I did open an issue which sounds similar: Significant_terms - select on basis of quantities other than doc count. · Issue #12309 · elastic/elasticsearch · GitHub
That pre-dates pipeline aggregations so the idea was to access properties of docs as part of the aggregation phase rather than post-processing aggregation values using a pipeline agg.
I'm not sure things like average prices make sense to compare with the significance algorithms. For me significance is a measure of how "bought-into" something another thing is. Set overlaps. Your "significant other" is someone you both invest a lot of time with. A "significant investor" is someone who has invested a large (to you and them) sum of money. A significant term is something like h5n1 that only seems to appear in a particular context e.g. "bird flu" search results. These are measures of a set size (total time, total money and total docs) and the extent to which they overlap with another set. So sums of a resource. We can visualize the size of set intersections as Venn diagrams.
Averages maxs or mins I suspect are of less use as they don't quantify the size of the set and are therefore of less use in examining set overlaps.