The Marketing side of my brain says:
Cost of materials x 3 - retail
Cost of materials x 2 - wholesale
The Family side of my brain says:
-Christmas gift
-Birthday gift
-Sell it to her at cost, IF she really wants to buy it from you. I remember my friend's grandmother paying him $25 to reset the clock on her VCR...not a huge task, but she wanted to give him money. (Families are weird!) :)