Prompt price can be set on non-inventory products only,to set up a prompt for price Quick Pick Panel.

First you should add a non-inventory product ( if you already have the product, you can skip the first step ).

From Catalog>>Products>>Add new>> fill in the product info and don't forget to apply both of the main settings: 

1) Non-Inventory Product on Product type drop-down.

2)select/check on prompt for price option.

after setting up our product go to Setting >>from the 'Sales' column list, Select 'Quick Pick'>> Add New>> Enter the Required fields:

• Panel Title:  this setting will display the title on panel.
• Panel Order: orders/ priorities the quick pick panels from the important to the least ones. (note function isn't working well now because it displays the newest QP panel that you just added)
• Heading Text Color: function isn't working properly for now.
• Panel Header Color:
• Panel Item Button: in this section you can add multiply items to the panel, simply fill in the item name and select the proper settings to it.

Once you have  saved the new Quick Pick option, the following product will displayed on the front register in the Quick Pick Panel tab.