Avoid this kind of useless shop-savings extensions that in facts can spy what you are looking on the internet, it's just collecting informations on you to profile you and similar customers to finally target ads/products/services. That's desguished spyware in counterpart to provide you a pretended nice service for free.

And just about the service provided: this kind of extensions (lots of similar exist like this one) can modify the webpages on-the-fly and also can censure some parts or search results to guide you to buy to a specific shop... instead of a concurrent. And guess who is paying the extension editor to do that? Sellers?
Just look at what this extension is requiring at the Permissions part...

Mind again before adding browser extensions!

in 17 amazon object buy with this extension none of them have offer me even 10% off.

AVG is owned by Avast. Avast was recently exposed in a Vice/PCMag report which revealed that it sold web browsing data, including the sites you visit and the links you click, to third parties.

Дважды на одни грабли? Нeт, спасибо.