I've found it can do a lot, especially if your app is for a niche market like the OP's. When you go to a conference or a trade show, you're surrounded by people who will buy your App. It doesn't get any better than that when it comes to marketing. Good reviews only help if people find your app on the app store to read them.
The best marketing you can get is through reviews and word of mouth. In my mind, that money is better spent on improving the product.