why can't computers handle the buying & selling and come up with 1 price for everything? why does the ES need a .25 spread? why do stocks sometimes have huge spreads? i know it's because of volatility, but so what. a computer should come up with 1 price. if i want to sell a baseball card, i don't have a bid and an ask. it will sell for the price i decide to sell it for. why should the markets be any different? why can't we make this all electronic and have 1 price for everything?