Those prices sound very typical (and possibly even low) for the cost of attending most trade shows. And if you add in travel, lodging, meals and display/promotional material costs, it's not hard to put a few thousand into a single show.
Advertising costs are all over the map, depending on circulation and each individual source.
In both cases, remember that many of the other advertisers are bigger firms. If you gross $100,000, $800 sounds like a lot; if you make $10 million, $800 is petty cash. While there's something to be said for putting your name up next to the other big players, I think you're right about looking for other ways to reach your target audience.

