Even if you use a barcode there's no reason why the price can't be entered in directly or modified at the behest of the cashier. In the West we just don't trust our cashiers enough to do that sort of thing so we lock out that power ("Manager assistance needed at isle four!").
What the world needs right now is cashless payments that don't have absurd (>0.1%) transaction fees. I used to work at First Data (largest credit card processor) and you know how much it costs them to execute a credit card transaction? NOTHING. It's literally nothing.
It's not even a factor of, "we have this many servers in this many data centers and here's how much the electricity costs, divided by the total number of transactions in a given day." Why? Because every customer that uses First Data still pays a monthly fee that more than makes up for the cost of all the employees, data centers, software, etc etc.
If all First Data ever collected was that monthly fee they'd still be profitable (assuming all they did was handle credit card transactions).