Given GDP is a fake number that increases every time money is moved eg if you and a friend hand a $1 bill back and forwards a billion times you technically just increased the GDP by $1 billion dollars. I would say he definitely increases the GDP, but the accuracy of pricing is, well relative to say the least, if we didn’t have high speed traders we couldn’t be that “accurate” so if this is true it’s still unnecessary since the average man can’t spend money at the speed of light through a distance optimized path. As far as reducing the price of anything, uh no, no that would be a stretch of even the most generous of readings.