The cost price is not just the purchase price; it also includes transaction fees. For example, in the US stock market, the minimum fee per transaction is $1.98. If your transaction amount is small or you buy only a few shares, the fees will significantly increase the cost price. For instance, suppose you buy 1 share of Santander Bank stock at $4.64, plus a $1.98 fee, your cost per share will become $6.62. Therefore, it is recommended to trade larger quantities or higher-priced stocks so that the relative transaction costs are spread out, reducing the impact on the cost price.