When Amazon is out of stock on an item, sometimes they offer the item for a lower price until it comes back in stock. Although Amazon is out of Photomatix Pro 4 at the moment (regularly $99), it is available for $77.52 and will ship when in stock.
I know Photomatix Pro has its fans, but with Nik HDR Efex Pro 2 available with the entire Nik Suite at 50% more I find it hard to justify that price for Photomatix alone.
Well here's the thing--when I checked to see if Nik Efex Pro would work with Photoshop Elements 10, what I found indicated it wouldn't work. Is Efex Pro a stand-alone type of program? I don't know enough about it.
Do you have Lightroom or just Elements? You can invoke it from Lightroom. Unfortunately the Nik stuff won't work alone and relies on having either Lightroom, PS or PSE (in the case of the other tools) to run on. I suspect it has something to do with what Elements cannot do with multiple images and layers. I just tried to see if I could invoke it somehow from both Elements 11 and the Organizer and no dice. Didn't know that.