There really isn't a need to increase prices on .pdf's by that much, as they eliminate the need to pay for the traditional infrastructure (that supports physical books). The cost to produce each incremental (unit cost) .pdf is a fraction of a cent.
Now, if they invested heavily in upgrading their computer hardware and software, then an increase is justified, but as far as I'm aware, they only upgraded the online "storefront" that supports all of their products, not just the pdfs.
Yes, I saw their reasoning about increased production cost, but I think $10 per unit is a bit much.
Nonetheless, I'll keep on purchasing things from Paizo, but at a slower rate, and be more inclined to really think about the purchase before I pull the trigger.