What do these Eachine sellers get out of doing this anyway? Do they use our money for the 2 weeks that they have it?
Perhaps, but more likely they are just trying to make a buck selling something they don't normally stock, thinking (hoping) they can get it, to send on to a customer at a moments notice, which is probably normally the case. But in an instance like this where that something becomes suddenly popular and no longer available, they most likely hope to wait it out, until they can take delivery from the next batch, which is what I think we are experiencing here.
Because Jin is in with the production source, he still has, or continues to have, these models to sell, but these other outlets are awaiting having their orders filled, first come first served, but Jin is on the ground floor with the production.
That's my take anyway.