I think your product has to be very related to your hub and you shouldn't overdo it. I make some Amazon money every month. Ebay just sucks. If you have those capsules, I'd just remove them unless there's a very specific seller or reason you have them there.
With Amazon, I tend to use my own descriptions or blurb with the product to say why I use it and how it helped with - whatever my hub is about. I also put the product right within the part of the hub that is relevant to that product for the most part. This has helped me make sales.
What I need to do is some hubs for some bigger ticket items. I sell a lot of small stuff - but it certainly isn't very much money. For me, I've never put more than 2 items in hub because more than that I think looks to "sales pitchy". It also depends on the type of the hub though I suppose. Nothing I have written needs more than one or two.