This was my first addon purchase for XenForo, after searching for quite some time. I did a lot of research on shop/item systems, and DBTech's is honestly the best out there right now.
It was extremely easy to configure and set up, and the language is simple to understand for myself, a native English speaker who does not know too much of XenForo's systems or code yet.
I also purchased DBTech's Credit system, which implemented into this addon with pretty much 100% ease.
I would definitely recommend you check this addon out, along with all of DBTech's other addons!
Once you provide me with the links to the support tickets you've created, I'll investigate why they haven't been resolved yet.