Sometimes you just have to give up on AdWords for a product or niche.
I don’t usually like to recommend “giving up”. But after trying ALL the tricks, you may have to declare it to not work.
For example, I was helping a client advertise hammocks. But we eventually had to punt on it. It was a rare case where nearly all of the searches were for “hammock” and “hammocks” and the price was outrageous (i.e. unprofitable) per click. Plus content and placement targeting wasn’t much better. Only good for doing very infrequent sales from off-the-beaten path keywords and content sites.
(note: normally I don’t tell a client’s niche, but in this case he is pretty much abandoning it on AdWords, so he’s cool with me “giving it away”)
Though most of the time when someone is looking at this situation it’s because they don’t know how to do Adwords well. But once in a great while even a master Adwords advertiser has to say “time to move on and pick something else”.
Luckily for the client this was just a test, and he wants to go on to the next niche.