Bump it to cover your costs. All of our costs are going up all the time and in that light, so must the cost to the customer.
I used to charge for the size of the image PLUS the border of white around it and realized that, like you, i'm throwing away paper from a roll. So now, like I do with glass, I charge by what the piece comes from.
A 19x32 piece of glass has to come out of a 24x36 so that is what is charged.
A 19x32 print including white border would have to come out of a 36" roll so that size is what is used to figure the cost... 19x36.
Think about how to charge for something that is 7x37?? That can only come out of a piece of 32X40 glass. I do find it hard to charge for the whole piece of 32x40 glass so I charge for half. Either way, my materials cost are more than covered.
Yeah, people wanting one 8x10 print and I only have a 17" roll... I charge min of $15. Still not really worth the time to make that print, tho.