If your contacts are not appearing in your Mac's Contacts app after performing an export in iExplorer, then it's most likely caused by choosing to not allow iExplorer to access your contacts which is a new 10.8 and 10.9 dialog when opening an app for the first time. To resolve this and give iExplorer access to your contacts, you can follow these steps:
 

1. Quit iExplorer and open System Preferences
2. Click on Security & Privacy
3. Click the Privacy tab (and unlock the Admin lock in the lower left corner)
4. Highlight Contacts on the left and check the box next to iExplorer on the right
5. Reopen iExplorer and try exporting your contacts again.

The Apple support article below explains more about this:

http://support.apple.com/kb/ht5370