For example if user selects country as USA from a drop down menu, it need to display 200US$ in the payment option automatically
Hey,
You can achieve that using code.
Use an event handler, to react to a change in the drop down selection: Dropdown - Velo API Reference - Wix.com
And in reaction to this change event, change the payment option display (not sure how you implemented it so i can’t tell you how to change it’s value.
Good Luck,
Itai