Hi,
In average, implementing an extension takes 4 hours of our support time, but it depends on the complexity of the particular component. For pricing please see:
www.artio.net/e-shop/support-services/joomla-support-1h
Our JoomSEF 3 extension for JCal Pro is quite old, so the URLs structure could have changed significantly since that in the latest version of JCal Pro for Joomla 2.5 and 3. Since JCal Pro is a paid component and we don't currently have a development license for it and we had no requests for it, we haven't implemented an extension for JoomSEF 4 yet.