Ouch

I've just finished a project for a client that should have taken about 3 hours and actually took 3 days. It's often difficult to work with demanding clients. I have a reputation as someone who delivers high quality work, so I'm often forced to accede to any demands the client makes, however unreasonable, to protect that reputation.
As this client was particularly demending the last three days have netted me a grand total of around $90 - about $3.75 an hour. The only way I can convince myself that it wasn't half a week wasted is in the fact that the client should spread the word that I've been extremely accommodating.
The question, then, is where should we draw the line? There must be a point at which reputation building becomes untenable from a financial point of view. After all, I can't pay my bills with plaudits.