This is a sore subject for many artists, and The Oatmeal summed up the essence of it all.

(Click the picture!)
The other day I was asked to do a commissioned illustration for a friend. The piece is for an album cover for one of his music projects. He was up-front about there not being much in way of money as payment for this (as it is a bit of a niche-album with a fairly small audience, myself included).
I am – basically – doing this for exposure. And I’m fine with that. Why? Well…
As of right now, about 10 people on the planet are aware of my art. I’m not exposed – at all. I have no exposure to refer people to, other than this website, my facebook page, my instagram and my youtube-channel. I am working on changing that fact, but as it stands – right now – I need all the exposure I can get. If I am ever to sell a piece of art, I need people to be aware of my existence as an artist: I need exposure.
Let me be absolutely crystal clear: My friend did not assume I would do this for free / for exposure – at all.
I did – however – suggest a sort of deal for my commission work. A commission for commission, if you will: I asked my friend to make a snippet of music I could use for my YouTube-videos in exchange for me creating album art. And I made sure to say it would be “as payment” for the commission. My art will get exposure, and his music project will get exposure, as he will be credited wherever and whenever I use the music.
So – why is this whole for exposure business such a sore subject for artists? If you ask an artist – who makes a living through their art – to do something, that artist will charge you for it. It’s their livelihood – it’s what puts food on their table. Be prepared to pay for art, that’s all I’m saying.
The artist can choose to do something for free / for exposure, but it’s the artist’s call – not yours.