Had a client that was incredibly cost sensitive from the get go.
They recently sent me a brief for a complicated writing project. I began, and it became clear that the scope of the project was larger than I realized.
Me: This is a much bigger job than I expected. I'm going to have to incrementally increase my quote.
Client: Fine, I guess.
Eventually I finished the project. She sent me a number of small revisions - she was very exacting - and I made everything even though I was already over my budgeted time.
After sending in my invoice, I got this back from the client:
Client: It took me two hours to look at what you sent. Normally it would take 10-15 minutes. Perhaps we can compromise and I'll pay you half of what we agreed?
It took you longer because it was a big project - that doesn't mean you get to pay me less.