It would be very hard for anyone to know unless they saw boxes full of all parts coming from a local machine shop. While I don't think VPI is top of the heap in precision and while I cannot understand how this product is so cheap, this is not any sort of "hard evidence" they are made in China.
Lots of manufacturers lie about product being made in USA, implying parts are made here too. You would be surprised. Yet, that means nothing about VPI. He may be real clever about getting cheap prices from US machine shops based on quantity and long term relationships.