This works really well and lets me sort by unit price on amazon, across multiple pages. Brilliant, simple UI and functionality.
The addon contains code which appears to be unused, which adds (presumably) the author's own amazon associate tracking tag `tag=frx2q5di0orv-20` to every amazon product URL. But to be clear I'll repeat myself: that code is currently commented, and it performs only what it advertises. As an aside, the code is nicely written.
Would be 5 stars if:
(1) The source repository was public; and
(2) The author makes a clear stated commitment to avoid adding any tracking or associate links, cookies or other devices without an explicit "opt-in"

This looks to be very promising. Hoping the developer keeps up the good work!

Note: The add-on is shown as 'Experimental' right now. Great potential here.
This is the only add-on that I've come across capable of interacting with Amazon recently. The results are still hit or miss, but I don't feel like I need to browse through 20 pages just to find decent results.