[stomachmonkey]

The problem with what you did is you opened the door for, "If I had known how much extra it was gonna cost I might have said forget it."

By not letting them know up front you basically wrote a blank check with their money.

I know you are not really profiting from the extra cost but it is their money that you spent without their consent.

If they were not friends you could find yourself in a bad situation. There are people that would not pay you based on lack of up front additional costs and if you took them to small claims court over it you'd probably lose.

It really is not the right thing to do for yourself or the client.