Some embassies issue an income document. It gets accepted instead of the 400k. I did it twice (from the Netherlands) since I dont have a bank account yet. But can also be a pain process. Needs to be legalized etc. And immigration doesnt like it. They will still try to make some money by saying they know agents for a bank account.
The problem with it is, at least my experience, that they seem to make it extra hard if you dont use one. Try to push you into the direction of an agent they know. They love for you to use one, for obvious reasons. I rather take the hard route. It gets easier over the years and at least you know what is going on with the paperwork.