It's a number I found some time ago that on further investigation appears to be quite wrong as you say. It seems it's closer to 1tn USD annually, which would rank around number 16 in world GDP tables.

Edit because HN isn't allowing a reply: these numbers are industry revenue, not profit.

    https://www.bcgperspectives.com/content/articles/financial_institutions_pricing_global_payments_2014_capturing_next_level_value/
    http://data.worldbank.org/indicator/NY.GDP.MKTP.CD?order=wbapi_data_value_2013+wbapi_data_value+wbapi_data_value-last&sort=desc