Assuming you have a Global Pass:

The interrail planner does not display prices because there are no costs when you use the pass other than reservations, and when necessary the planner shows those costs.

If you want to know the retail cost of any journey you need to use one of the many rail planners  on the internet.

The cost for what? Reservations? That depens on what type of train you take. Most towns can be reached by reservation free trains.

Please give some more details. Then you will get better answers.