Google ads make absolutely no sense financially. Even for high value items. I recently bought some ads in hope very specific terms that see almost no search traffic will be cheaper (we're talking few hundred searches a month from whole of EU). Google wanted £1.5 per click through.

When I set a reasonable cost (0.1£) I got either nothing or generic keywords (which I added as a test). I'm pretty sure no one is actually bidding on these niche keywords as there are no ads shown on them ever.

Google simply decides not to sell unless you pay an exorbitant amount.