Sorry, missed your answer. The scare quotes around "cost" are just to underline the negative connotations in the term. If it turns out their are large overall

Sorry, missed your answer. The scare quotes around "cost" are just to underline the negative connotations in the term. If it turns out their are large overall gains from their activity, I feel it would be a bit disingenuous to talk about their "cost" if they're bringing more value to the economy than they're taking away. Anyway, I don't think your analysis is sufficient to answer my question. There are second order effects beyond what happens to people involved in the trading of securities. Better market efficiency means better pricing of securities, which has effects on the returns of equity financing, which in turn could mean higher growth at a higher level. To be fair, it's a pretty complex question and I wasn't expecting a precise answer, but references to papers that might have been written on the subject would have been interesting.