The total cost for Vietjet is around $200,000 USD for foreigners. It could be less if you went to a CAAV approved flying school for your CPL and IR.
The current batch of VJ cadets who bought their way in in late 2019 are still sitting at home due to the border closures. I would imagine the stress and anxiety for them must be overwhelming with all that money on the line... money they could very easily never get back if VJ decides to pull the plug.