I"m having a hell of a time with Google Shopping. I set up an Adwords campaign ("Adwords Product Campaign") for my products from Google Merchant Center. All of the products in the Merchant Center are ones that I've run Adwords ads for previously.
The Merchant Center thinks that these products violate Adwords weapons policies (they don't), and so they're disapproved for Product Ads. Because they're disapproved, my Adwords "Adwords Product Campaign" with the Merchant Center products isn't being displayed. They were showing up in September, and I was paying on average 13 cents a click. Then they stopped showing them completely.
Well, I have another Adwords campaign for some very expensive scopes, and I have to bid $1 or more to get on the first page. Even at that, I don't get many clicks on these Adwords ads, but I do get clicks from the search network, which includes Google Shopping, but instead of paying the 13 cents a click I was paying in September for listings in Google Shopping, I'm paying the $1 a click from the expensive scopes Adwords campaign.
If you can make sense out of all that, you're a whole lot smarter than me.