This is a great lesson for everyone, to know what works with them and what does not, especially with their overseas schedulers (if you can call them that). You can't argue their pricing with them AT ALL. Not directly, anyway. Instead of saying I can't do it for that price or your prices haven't changed in 20 years you have to say "I'm sooooooo sorrrrrrry, I cannnnnooooott afffffffooooorrrrrrdddd to do it for THAT" and then you have to laugh a little giggle and then shut up. They need to believe that they are in control of the haggling. Let THEM beef up the price. Don't specifically ask for more unless they ask you what it will take. To them, that is disrespectful. The fact that you are silent and have not hung up the phone says that you are willing to haggle to them. When they raise the price and it's still not enough for you, you have to say something like "Oh, wow (or whatever your semi-surprised to see the price go up that much response is) that is more money" and then shut up. They will escalate the price until it either meets what you need or they will ask you. If they ask you, tell them "$20" (or whatever your price is) is a very serious, louder and stern voice. Then shut up. It's a dance of humbleness that needs to be learned and practiced. It's not just this msc. Most msc won't deactivate you unless you've done something very egregious, but this one will, and can, for simply not negotiating with humility.
As far as the pricing not going up, that is true for most, if not all msc. As anyone can see from the video link I posted from the mspa's rep providing information, training and a list of variables for msc to learn how to keep their pricing down and how to get US mystery shoppers to do their assignments for peanuts, we need to learn to do the same thing! But we need to learn the dance that keeps the illusion that they are in control and that they expect.