Actually, let me bring a typical example to you:
"Amazing Costume Designer Needed ...
... I can't pay you. But what you'll get is: all costuming credit, copies of the images for your portfolio, and the possibility of being part of a potentially amazing project..."
It's one thing to ask an amateur or complete beginner to work for free. Even this is not quite right. But to ask for "amazing" or "experienced" or "expert" or "talented" or "published" Artist to work for No Pay - I just don't even know what to say. It's really disheartening.
OK, Discount and Free are two different issues, and I believe I've ranted about Free enough, so I'll turn now to Discount.
I will give an immediate discount for photography services for a limited number of reasons:
1. The client is my friend
2. Non-profit gigs that are too extensive to do entirely for free
And upon consultation, possibly:
3. Guarantee of repeat hire several times within a year
4. The chance to shoot a really really unique subject, such as Sheep Cheese Making (with Lambs included in the shoot) or the Rubik's Cube World Championships. Actually, I'd do these last 2 things for free, they are that awesome.
I know people don't mean to be insulting. But it's really insulting. I've worked really hard to get to where I am. I use way expensive equipment. My photographic eye can make trash into art. I think my rates are incredibly reasonable already. In case you're wondering, I won't be photographing the fore-mentioned event.