From what I understand, Amazon sales are reported through Amazon, not HubPages. The way Amazon reports things is by the Associate Tracking ID (ending in -20), and by link type. So you can create a different associate tracking ID for Hubpages to see how well it is doing compared to other sites you may promote the products on, but you won't be able to narrow it down any further. On a webpage, you could have different tracking IDs for different parts of your site, or even for every product you promoted if you wanted to go that in depth.
I don't know about other sites, but Squidoo shows you the click-outs for your pages, which lets me see which products people are actually clicking on and then I'm able to determine whether the click rate is rising or falling for those products.
Sorry I couldn't be of more help.