For that matter we don't even have a good characterization of how much of the daily transaction volume is in real commerce and how much is just zero-sum arbitrage and gaming like Satoshi-dice and Mt.Gox other then that were very sure they are the vast majority.
There is fragmentary accurate data, like an analysis of SR transactions that estimated its commercial volume during 4 months last year, the total sales of bitcoisnstore in 6 months, or the published earnings of Satoshi-Dice. If you combine all that kind of data, and apply the growth rates shown by other indicators correcting them by maturity of each market, you can get at least maximum values with a high degree of confidence.
Using that techniques I obtain that during March the maximum commercial volume was $31m, split in 7,6% drugs, 84,4% casinos and a very optimistic 9% for retail. Gaming is an internal industry and should be counted even if its a zero-sum and does not create value. Exchanges are excluded because they are just connections to other currencies, and we would be counting twice the commercial transactions (entry/exit).
