If you find $100 to be steep, don't do it. Use that money on a safer experiment. I don't think it's safe because the Google Apps Marketplace is the only marketplace that I know that does not disclose the popularity of it's items.
Otherwise try it and report back on your success!
If you have an extremely good app or if you are one of the big entities, I would say big NO. I have couple apps in the market (both in Appstore and App Market) and I can tell you from my experience, it's not worth time and effort you would put in. I can put in an app in Apple's Appstore and without doing much marketing, I can have 3-5 paid downloads a day. If I make it FREE, I will couple hundreds a day download easily. Now on Android's App Market, forget about the paid app, I don't even a single download even on the free one. Of course, if you do some marketing you get some free downloads. I own both iOS and Android devices. As an IT person, I love the Android phone. It's truly a smart phone and most Android users use it as such but iPhone/iTouch/iPad are mostly entertaining devices. That doesn't mean one is superior than the other. They are better and different in their own ways. Android users and iPhone users are different. They download different types of product on their devices.
Now on the pain of developing for Android. Developing the code is easy but testing and making the graphics show up nicely aligned for all Android devices is next to impossible and good luck with that. It's not fun. I am not a graphics designer and it's an extra challenge for me.
I can't speak of my own experience with the Google Apps Marketplace (yet). And there's not a whole lot of concrete/up-to-date info out there about this but I convinced myself that it's worth giving it a try.
Here are a few claims from the Google Apps Marketplace's success stories that indicate it's worth it at least for some types of apps:
"Since the launch, we've been averaging over 1,000 new business sign-ups per week through the Marketplace - double our previous weekly rate..."You can visit the linked page for the full quotes.
"We have seen a 500% increase in the number of seats being trialled by businesses since joining the Google Apps Marketplace..."
I found very few relevant posts that mention good success though. Here's one: http://blog.metadot.com/2012/12/google-apps-developers-how-to-get-more.html