I always called BS on this to. So I stopped and did the math myself.
If you compare the peak years of TSR when they were putting out the most D&D content and accessories (the mid '90s) with last year from Paizo, the latter released more (and will again this year). Even if you include the Forgotten Realms in the mix - fair since a third of Paizo's material is specific to their campaign setting - then Paizo is producing more.
Except... it stops working if you add Dragon and Dungeon to the mix. That was still published by TSR at the time and adds a staggering amount of pages to this mix. And so much of Pathfinder (the monthly APs and Player Companion volumes) are what they used to do for the magazine.
Call me surprised. Now let's take a look at what Paizo published for Pathfinder in 2014. I'm just going to use Amazon in the "Pathfinder Game" category under books and then sort by publication date and then I'm visually sorting by publisher and sticking to Paizo. I'll also double-check the Paizo web-site, but there is probably some margin of error here.
BOOKS
Hardcover Rule Books (3): Monster Codex, Advanced Class Guide, Inner Sea Gods
Campaign Setting sourcebooks (7): Ships of the Inner Sea, Undead Unleashed, Technology Guide, Numeria, Occult Mysteries, Inner Sea Combat, Osirion
Adventure Path (12): Iron Gods 1-4; Mummy's Mark: 1-6; Wrath of the Righteous 5-6
Player Companion (12): Ranged Tactics Toolbox, Advanced Class Origins, Champions of Corruption, People of the Stars, People of the River, Blood of the Elements, Harrow Handbook, Alchemy Manual, Undead Slayer's Handbook ,Champions of Balance, Bastards of Golarion, People of the Sands
Modules (3): Plunder & Peril, Emerald Spire Superdungeon (hardcover), Tears at Bitter Manor
OTHER STUFF
Flip-Mat (lots): Red Light District, Tech Dungeon, a bunch more....hard to tell which year they were made.
Map Pack (1+): Starship Corridors; see above
Tales: Nightblade, Reign of Stars, Crusader Road, Skinwalkers, Dagger of Trust, Redemption Engine
Adventure Card Game Class Decks: Wizard, Bard, Cleric, Sorcerer, Ranger, Rogue, Fighter
Adventure Card Game: Skull & Shackles 2 and 3
Pawns: Bestiary Boxes 3 and 4, Wrath of the Righteous
So yeah, that's a lot of stuff. Just counting actual print books, that's a total of 37 - or 3/month. Now of course those 37 aren't all created equal, and one of the things I like about what Paizo has done is that they "only" come out with about 3 big hardcovers per year. Compare that to the 10+ of the 3E/4E era. Of course those 10+ included setting material and some adventures, but still. Didn't someone count a total of 100 hardcovers in the 3E era?
In the end it doesn't matter to me how much product comes out, as long as there is
some and as long as it is good quality. I won't buy everything but I would buy more than what is presumably planned.