> there is no stock market that invests tens of millions of dollars in stopping people buying stocks
There definitely are -- everything from margin limitations, maintenance requirements, regulatory bodies, and counter party risk.
> It doesn't improve efficiency in any way because the price you are taking is known.
The price you are taking when you buy a stock is also known to all participants. Just like sports betting, the marketmaker (bookie) is profiting between the bid & ask spread.
There definitely are -- everything from margin limitations, maintenance requirements, regulatory bodies, and counter party risk.
> It doesn't improve efficiency in any way because the price you are taking is known.
The price you are taking when you buy a stock is also known to all participants. Just like sports betting, the marketmaker (bookie) is profiting between the bid & ask spread.