90% of all vaping hardware is manufactured in China, buying from China vendors can almost guarantee lower prices compared to US vendors due to it being imported electronics. However, some of the further engineering, modifications, etc can come from buying from US vendors. I've bought hundreds of dollars of perfectly good working hardware from China vendors, all of which were cheaper than buying from the US.
Juice is a little different story. So far I personally haven't found any China made juices to be as remotely good as some of the juices made here in the US..
Dekang tobacco flavored juice is Ok, but non-tobacco flavor seems very acidic and syrupy.. After trying flavors from fuzionvapor.com & aliceinvapeland.com(both from the US), I haven't touched tobacco flavor juice & have no future desire to. Blueberry pie with banana, tart cherry with lemon lime, those are my all day vapes now.
~Vaping is a lifestyle~