professional response to ridiculous offers?

I know I read on a post I can't find right now, a very professional and clear response to someone offering to pay half the going rate for twice the kids, or something like that. Anyway, I had my first festival last weekend (yay! huge success) and the organizer just contacted me to ask me to paint one day/week at the town summer camp for $75 a day (4 hours but they did include a 20 minute break ). I don't want to offend her as I believe she is more clueless than rude, but I do want her to understand why I couldn't even consider that offer. Does anyone remember the thread? or have suggestions on wording?
thanks guys

I do not remember some of the amazing succinct responses on another thread.
I know there are some brilliant, eloquent face painters and I cannot wait to hear from them. I am the person who would be saying, "I'll get back to you in a half an hour when I can think of something smart to say."

My visceral response is, "I am sorry. I cannot afford to pay to work for you." Figure out how much it costs you in paint for every hour of painting, plus travel, event insurance, educational upgrades, glitter, jewels, brushes, carrying case, spray bottles, rubbing alcohol, water containers, sponges... and just adding minimum wage to barely cover your presence comes to more than you are being offered per hour. You are being paid for your artistry. They cannot possibly pay you what you are worth artistically, so they should at least offer to actually pay you what you ask, and not make you pay to paint for them. (Even the craptastic Craigslist painters around here have the going rate of $35-$45/hour. I think your work is head and shoulders above the work I see posted on their advertisements).
They could not purchase the just the supplies to paint for four hours for less than $150.
$80 for two 12 color palettes (and you have more colors than 12)
$40 for one each of black and white
$30 for six medium quality brushes (I am sure you have more than six brushes)
$8 cosmetic glitter
$3 70% Isopropyl Alcohol to sanitize brushes between children
$6 sponges cut down into usable pieces as you use one sponge per child
$5 Q-tips
$10 baby wipes
$3 hand sanitizer
Of course, I am using Canadian prices as a guideline. I know that the prices are cheaper in the States, and they would have to pay for shipping to get the supplies, or the legwork and mileage to drive to pick out supplies.

xoxo

If you look at them offering you an hourly rate to work at camp... it isn't a bad rate of pay. HOWEVER... it isn't going to cover you as an independent contractor. Just tell her what your rates are, then when she asks or comments on how much that is, explain why.

I would consider a counter offer if it met the following criteria:

It was a repeating gig for a specified time, AND
It was on a week day when I had nothing else going on AND
Every child took home a card to parents AND
It meant getting practice and photos.

My counter offer would probably be a reduced rate for a day of the week which doesn't usually have parties scheduled, such as a Tuesday. I would provide the camp with a photo permission slip to send home to parents.

I just let my clients know that if they would like to hire me weekly then, I can offer them an XX dollar amount discount. Then, I have them pay a booking fee and fill out a service agreement for X amount of weeks. I include the dates and times in the service agreement so it is solid.
If they question your rates then, you should direct them to your website where your rates are in black and white so they can see for themselves how much you normally charge. Usually that clears it up for them.