Sketch and Principle versions. Pair work. How costly is it?

Question

User interface

How do versions of these programs depend on each other? Do I need to buy new versions of programs every time so that they work in pairs? How much is it?

Answer 1

I have not updated Principle for a long time, updating Sketch and there were no problems. You do not pay for updates of purchased programs. The sketch costs $99, it's written on its website))