How much would you charge a friend to write out your invitation envelopes?

So basically I asked my friend who has really good handwriting and does some good lettering to write out the addresses on my wedding invitation envelopes. She isn't a professional calligrapher but I asked her how much she would charge to write out around 70 addresses and she said she doesn't have a set price but would appreciate an Amazon gift card. She didn't say an amount so what do you guys think would be reasonable? I would have rather just had a set price instead of coming up with one on my own and risking looking cheap/not giving enough. For reference, it will just be for the main addresses, not the return address. via /r/weddingplanning http://ift.tt/2sFfBIk