[burntoutfire]

Just say - "I'm sorry, but it doesn't make sense for me to take a 50% pay cut to change a job. If anything, changing job comes with many risks, and I would expect a pay increase to compensate for that". If they really want you, they'll budge. If they don't (they believe you're easily replaceable with someone else in the hiring pipeline), there's nothing you can say to change their mind. (This is under assumption that you've sold yourself well during the interview and they are already aware of the full value you can bring to them.)

I'm also from a low-cost country, and recently got a new remote job paying upwards of $150k, using exactly the technique I described above. They just didn't have alternatives, and knew that similar people to me probably wouldn't work for much less anyway.