In my experience, the 'revenue potential' $'s bear no relation at all to the popularity of a hub. My best traffic hubs have $$. I've noticed that a couple of the hubs on making money online have $$$, and ones about holidays and buying property have $$$$. It seems that the $$$'s metric is not very sophisticated and probably just refers to the expected cost per click of ads on the page. And it's all very well getting high cost per click pages, but if you don't get any traffic then it is useless. Plus, I use the Hubpages ad-program which (though I am not totally convinced by this) is more based on total page impressions than actual earnings from that page.
So I personally wouldn't pay much attention to this metric. You are much better trying to get high traffic articles by using keyword tools or your own intuition.