How do I alter pricing in payment settings?

To change the prices you need to click on the payment section, wizard icon and the edit button on the product you need to update: 

Once you enter on the product settings you will see the price box, if it's blocked then you will need to change the prices you have set up on the quantity option: 

You will find the quantity options at the bottom of the wizard: 

Once you click on the edit button, you will find the prices each quantity has: 

Hope this helps.