I just checked and yesterday was about 40% better in terms of revenue than my average. It does seem like a lot of people got a nice surprise. I hope that it is the same for the rest of the month as revenue for the month is running behind July's numbers.
Google has done its regular "smart pricing" update based on conversion data (and whatever else they use), and we're seeing the effect of that recalculation.
This sounds very feasible, as the changes are marked enough to note a shift in the pricing.