I've never paid import taxes or duties on any flight sim hardware I've imported from China or Europe to US. Canada is a different matter, but US has an allowance under $800usd afaik for a lot of electronics. In the hotas world we often have to split orders at that point to stay below the $800 threshold.
The bigger question I think is the level of risk you are okay with on this. If it's anything like my ebay 4650G, whatever happens, you are completely on your own. Unless they really are selling a boxed product, it's probably a tray CPU, so basically no warranty from AMD.
When I had to RMA another CPU with AMD, they did require purchase receipt. So even if it's a china market boxed CPU, not sure how AMD NA (RMA center based in Miami iirc) will interpret that.