Customization single price option
Can someone tell me if it's possible to add a single fee for customization to an item. Example: I am selling tote bags for $8 each, but I want the customer to be able to add their name for a single extra fee of $10. So if they order one bag it's $8+$10 for customization, if they order 5 bags it's $40+$10 for customization. The customization I've seen so far wants to add the extra fee to each but I really don't want to do that. If it's possible, how??