Find places where your target market congregates, and find ways to target them individually.

I'd imagine your target market is generally deal-savvy. I also assume you've done research and determined that there's a portion of the market that is deal-savvy but doesn't like the "hunt" or the "chase" of tracking down the best deal themselves, and that that segment was worth making a product for. I'd advertise on sites which attract deal-savvy shoppers, like Woot and Slickdeals, both of which have their own advertising offerings and don't just use AdWords/DoubleClick.

You can't find a person when they're in the mood to go electronics shopping, but you can find the product they're looking for. I'd take out Google Adwords ads for brand names, product names and model numbers. Amazon and eBay affiliates do this in bulk already. Maybe don't choose the best sellers in a category, since those might be expensive spots, but maybe the second-tier products to start?