As Tom says each artist can calculate a unit cost for a disc, which will vary considerably depending on a range of factors. To sell below this price is to incur a loss; something one might decide to do, but not generally a good plan.

The calculation then becomes more subtle: is the artist one who wants to get his work better known (as AJC above) = downward pressure on price; is the evening's deal with the organiser one which leaves the artist with little to gain other than what can be made from merchandising = upward pressure; what price do the audience expect to pay, and will varying that price have a significant effect on sale numbers; the artist can reduce unit costs by selling more, but how many more potential buyers are out there, and how big a reduction.

Economic hard times are affecting us all, audiences and artists alike. I don't feel there can be a right to expect cheap goods at a performance, there are too many factors at play which may make it impossible, but of course I appreciate it when I find them.

Incidentally, the "Sultans" disc is back to £12.69 at Amazon now, damn them.