The costs of root canal therapy can vary depending on a number of factors, but most significantly it's dependent on the number of canals that need to be cleaned and filled. A straightforward case with a single canal and easy access will cost less than a molar tooth with 4 canals that has had previous root canal fillings that need to be removed first.
A CBCT scan pre-treatment can identify the number of canals and degree of difficulty before we even start drilling into the tooth. This improves predictability and shortens treatment time, which in turn brings the cost down.