There are a lot of key books that are really low on the list. I was most surprised that Marvel controlled such a huge % of the market, not often in the comic industry do one company have over 50% of the months sales.
I came across some article somewhere earlier this morning (sorry for being so vague, I just can't relocate it!) with a brief interview with Joe Quesada. They were lamenting the rise in book prices from $2.99 to $3.99. Obviously not all titles or publishers do this, but I think the smaller boutique or independent publishers are charging more in general. Maybe in these "economic times" people are sticking with the cheaper books so the larger companies like Marvel can rise in overall percentages.