I know what you are talking about with the prices. The publisher I really noticed this on was BLU. One of the books they first published (Black Knight) was only $9.99 while one I picked up a few weeks ago (Madness) was $14.99!! Talk about sticker shock. Of course there was at least one price hike between the two, but still there is only about 6 years difference between the publishing date of the two as well. I find that both a little sad and rather worrisome.
Blu (or rather TP) isn't the only one that has incerased their prices. I think everyone has, though they have increased them faster then others. I know that Viz has only gone up a buck, but then I think they are a more stable company.
As stated before I'm sure the economy played a part, increases in the cost of paper, gas for transport, what have you. I hadn't thought about the e-readers, but I'm sure that plays a part in things as well. Heck, I'm sure scanlations aren't helping anything either.
About the paper I did hear on another forum that TP (including BLU) had switched to a diferent paper that was cheaper, but got tons of complants about it (thin paper that tore really easy, and blury art work) and later switched back, or to something else. I know that I went and checked some of my earlier volumes of Kyo Kara Maoh, and found the page count about the same, but the thickness of the books were quite different.