It's good to hear that you are getting a lot of traffic with your Hubs, and that your success on HubPages is burgeoning as we speak. And while I would often recommend that you write more high quality Hubs, on very high paying keywords, I think now that this is simply not the case.
So instead, I'm going to inform you of the ratio in which HubPages calculates your earnings. With every 1,000 views that gain when on HubPages, you are only credited for around 600 of those views, and the rest go straight to HubPages. Why? Because they do need paying for their service too, and without this income split they couldn't possibly afford to maintain the site, and keep it running at optimum speed.
What does this mean for you? That while your Hubs may be gaining a lot of traffic at the moment, you need to be looking to either improving those Hubs, or integrating the Amazon widget, to maximise your potential income. (Or the Ebay widget.)
Hope this helps!