How to sell more then one coke

[Stainless Steel Refrigerator]

cant get my deals to be more then one coke no matter what i try, anyone know how to make it go up?

[Deathfromace]

progress more in the game and move up where people have more money and more desire to buy more

[Adam]

Each npc only buys some many $$ of drugs per day. Having more expensive product just means that they buy less.