[thelist] What would you do???

Well, the artist quoted you an estimate of 11 to 12 hours.  If he thought
that he was going to go over that estimate, he should have notified you
BEFORE going over that estimate, giving you a chance to make a decision of
go/no go.  Since you had been communicating with this company via email,
then you have their agreement in writing.  If I were in your situation I
would just say that you had agreed to the 12 hour maximum, plain and
simple.  They made the mistake, not you. 

I work for a consulting firm and this is the way we handle it all the
time.  If we do go over budget, then we simply eat the loss, and that is
often very costly. 

Anyway, that's my $0.02.

Good luck!

- larry