I can assure you that AA has dedicated circuits for their 800 service. The price per minute is around 1.5-8 cents per minute. They do have special network router features that may add a penny or two per call but one half an hour call will not cost AA more than 50 cents. Taxes run about 20% as well.

AA's biggest problem is that they have a huge volume of incoming calls. Banks, airlines, and insurance companies are some of the biggest users of Toll Free numbers around. Even if you go to VoIP you are just now getting under the penny per minute rate but you have to spend more money on terminating the call in special equipment. You would be lucky to save 3/10's of a cent. Assuming 50 million minutes a month in inbound Toll Free and you have a savings of around $150,000 a month. Figure in the time and effort involved in making the conversion to VoIP and you have very little reason to change if you are AA.