I suppose my question is better framed as - why is the cost of trading so high? Presumably the stock exchange will charge per transaction, but if I have 100bn invested across 10,000 equities, at a dollar a piece, that's 10M shares. If I make transactions of just 100 stocks per time, that's a whole refresh in 100,000 transactions. Do that 12 times a year at 5 dollars per transaction and I see a mere 6 million cost to look after 100bn in invested funds.

So ... What am I missing. Exchanges all use electronic trading now, Charles Schwann would give me 5 bucks per transaction.

Why does anyone pay percentages?