Discount brokerage firm Charles Schwab this week announced a $26 billion merger with TD Ameritrade that it says will make it more competitive amid a fierce financial industry price war. That may be one reason Schwab is also relocating its corporate headquarters from San Francisco to lower-cost-and-low-tax Texas.

Since its founding in 1973, Charles Schwab has grown into one of the nation’s largest brokerage firms by reducing the fees it charges to clients. In the 1970s Schwab charged about $70 per stock trade, which it cut...