Whats the most effective way to intergrate a javascript cost calculator to a specific node
You can use JS injector module


  Allows administrators to inject JS into the page output based on
  configurable rules. It's useful for adding simple JS tweaks without
  modifying a site's official theme - for example, a 'nighttime' color
  scheme could be added during certain hours. The JS is added using
  Drupal's standard drupal_add_js() function and respects page caching,
  etc.


or simply use drupal_add_js in body field with enabled PHP input mode and take a look at this page