The September issue of Gemaga costs ¥990. But look at all the amazing bonus content you get.
First and foremost is a download code for Atelier Meruru. The code gives you a costume for making Meruru look like Rorona.
You'll also get a bunch of Neptune Mk2 posters... none with Keiji Inafune, unfortunately.
Finally, depending on the shop that you buy, you'll get this forbidden Atelier Rorona poster.
See 4Gamer for further details.