When you buy from a vendor in China, unless you are buying a LOT, the shipping is usually much more than buying from a domestic retailer. If you pay extra (or buy more than a LOT), it will probably be shipped EMS. If not, it will go via China Registered Mail. EMS can take 3-4 weeks for delivery, China Registered Mail up to 2 months. If you're lucky. If you're not lucky, your package will get stopped by customs in China and returned to the seller (this happened with my 1st PV.) Most merchants in China will send it a second time for no additional cost. If it gets returned again, they will refund your money and you will have waited up to 4 months without your supplies.
If your package makes it through Chinese customs, it might get stopped by U.S. customs. Three years ago, the FDA was getting some packages seized on a semi-permanent basis. Today only a few get stopped and most of them are released in a few days.
When you buy from a U.S merchant, they have dealt with all that for you. Your items have already made it through customs and you can receive them in a few days. That's what you are paying for when you buy locally. The convenience. In addition, you are supporting domestic small business who have a vested interest in helping to keep vaping legal. State and Federal legislators and the FDA have no interest in what the people at Joye or Smoktech want. They don't vote here.
I do buy direct from China*. I even help with a co-op that buys from Health Cabin (and we spend so much our orders get sent via DHL.) But I also buy from U.S. websites and do not resent their making a reasonable living in return for getting me what I need quickly.
As for the current shortages. During the Chinese New Year nothing got shipped or built for 10 days. Now that it's over, the factories have to produce the products to send. While most U.S. vendors expected this and stocked up, lots of people were buying extra in case the FDA stopped the sale of PVs. All will be back to normal shortly.
*I don't buy e-liquid from China. Considering China's track record on consumer safety, I don't understand why people would buy something that is essentially a food product from there. But that's just me.