What Is The Cost For Invisalign Treatment?

What should I really pay for my Invisalign treatment? Hi, I am doing invisaligns and I now have to move halfway through my treatment This was at a cost of 6000, composed of a 1500 down payment and 250 monthly payments. I still have 2000 to pay. However, since I am moving I have to terminate my program with my current dentist . I have done 9 months already and I still have 9 months to go. My orthodontist suggested that I pay the last 2000 and she will hand over the remaining trays. It will then be up to me to correctly switch them every 2 weeks and also get a new orthodontist that can do regular checks and continue the treatment. I have done some research and asked a few orthodontist friends and they have told me that the actual cost of invisaligns to the dentist may range between 1000-3000, then you have to think about general revenue and other fees such as overhead fees. I feel it is not fair for me to pay the full 6000 if my dentist will not have to provide me any services for the last 9 months of my treatment. What would be a fair price I can try to negotiate with her so she can hand over the trays before my departure. Please let me know what you think. Thank you!