In May the price was ~450 USD/BTC, and on a good day BiTPay's presumed input wallet received over 2000 BTC. So, indeed, in May they were processing 1 million USD/day ... tops.
They haven t updated that number since then, though. Analysis of that wallet suggests that the USD volume that they have been processing has been decreasing with the BTC price.
AND a large fraction of that volume, as noted before, appears to be miners paying their bills, not Joe Public using bitcoins to buy stuff and services.
Realize that Bitpay is one of a few service provider in the market. Additionally understand that this Analysis is of one Bitpay wallet.