Looks like a great collaboration piece to me - the makers probably pay for placements and the publisher sends pics of approved headphones to an illustrator. Illustrators are usually paid a flat fee for a single piece.
Artwork done for a specific purpose is called Kaki-oroshi .
In my line of work (now and at Microsoft), I've seen rates for a single illustration ranging from 5000 yen (50 USD) to 100,000 yen (1000 USD).
I know there are many DC readers who do illustrations. Do you make pocket money from your work or make a living from it?
This is my fave girl in the book. Looks like Mio-chan. Gorgeous eyes. Will probably cut this leaf out and stick it on the wall.
How many of you put up posters? When I was a wee lad, I had a couple of posters up ^^;
Speaking of Zettai Ryouiki, J-list have this rather stylist T-shirt available for those who want to express how much they like that zone between where the stockings end and the bottom of the skirt starts.
Available now for 18.95 USD.