Of course your existing provider is going to try to charge you every dime they can, since you are leaving them. Depending on the size of your practice, and how many records, you may decide you want everything transferred automatically, nothing transferred automatically or somewhere in between.
If you are the type of subspecialty practice that sees patients for brief periods, then rarely ever again, you may not want to go through the expense. Simply keep your existing system, backing it up, etc, until the time period when you no longer need to keep them. If a previous patient does return, manually scan or enter those records into your new system.
If you are a busy primary care with patients staying with for dozens of years (and you see same day appts), you may want to bite the bullet and have all records automatically imported.
If your practice is somewhere in between, you might want to have only certain key items like demographics, office notes and labs transfer automatically.
I recommend thinking about the type of patients you see, and the impact of not having their records readily available in your new system. Try to evaluate if you transferred records internally, how many extra hours or temps you might need for this project. Then compare that with what the vendor is charging you to transfer that data to decide if it's worth it.
I've never seen an easy transition from 1 EHR to another EHR, but you can make it as painless as possible with proper advance planning.