You have not provided any detail on XenForo.com about what your addon does, or even previews of it.
Your website has images that are watermarked? (presumably because they have not been purchased for use).
Your website is not clear about the addon, are you charging me for the addon then also charging me 0.9% fees? Are you the payment provider or are they third party?
Your root domain "usersight.com" has no landing page or contents. I cannot find any additional information about who "UserSight" is; If I were to buy this addon, I would want to know that I can trust you because it is incredibly easy to get in the middle of a crypto transaction and hijack funds.
While I already have discovered that the Payment Processor is "cryptonator.com" and that they are the ones charging the fees, I personally feel that disclosing transaction fees as a selling point for your addon is confusing to the general audience you're selling to.
VersoBit said it all. But in case you have any further doubt, there are plenty of free services to setup Crypto payments who take a small pecentage and are nowhere near as shifty as this DEV is. STAY CLEAR!