Something tells me that you would have to break the book market down into much smaller segments in order for an analysis to be useful. For example:

Academic books are probably going to have the same volume, almost regardless of the price. Students have to pay. For researchers, it is a necessary expense.

The volume of popular novels may or may not respond to price, at least within a fairly large range. It is almost a mob mentality that drives these sales. On the other hand, this market segment is probably more prone to piracy than other market segments.

Unknown indie titles are probably the most likely to respond to price, simply because there is a higher risk involved in buying them. Yet that may lead to impulse buys, and unread impulse buys are unlikely to contribute to the sale of future titles by the author. Thus it may be a net long term loss.

Of course, it probably needs to be broken down much more than that. Readers of different types of books are going to respond differently at a psychological level. Everything that I've seen suggests that readers of genre titles are more prolific readers than those who read general fiction.

Sorry about the lack of numbers, but those seem to be closely guarded by the industry.