One difference, probably not related to what the flight attendant said, has to due with passenger taxes.
All domestic flights and all flights that start within Canada and Mexico that are within 225 miles of the USA are taxed at 7.5%. (This is in addition to other taxes on airline tickets). There is an exemption of this tax for the portion of the flight between Hawaii/Alaska and the mainland that is more than 3.45 miles from the mean low tide on the coast line. However, don’t think you are getting away with something because these same flights are also subject to a $7.50 tax.
As can seen below, airline fares have a multitude of taxes added.
The below is courtesy of the Delta Airlines web site.
U.S. Excise Tax
(aka U.S. Domestic Transportation Tax; U.S. Ticket Tax)
Percentage of fare; applies to flights within the continental United States or Canada/Mexico 225-mile buffer zones U.S. Domestic and International US 7.5%
Travel Facilities Tax
(aka Alaska/Hawaii Ticket Tax)
Applies to certain flight segments to or from Alaska or Hawaii U.S. Domestic and International US $7.50
U.S. Federal Segment Fee
Per-segment inflation-adjusted fee applicable to flights within the continental United States U.S. Domestic and International ZP $3.40
Passenger Facility Charge (PFC)
A maximum of 4 charges per itinerary applies to PFC-approved airports for facilities improvement U.S. Domestic and International XF up to $4.50
September 11th Security Fee
(aka U.S. Passenger Civil Aviation Security Fee)
U.S. government-assessed fee of $2.50 per U.S. enplanement per ticketed journey for security costs not to exceed $5.00 one-way or $10.00 round-trip U.S. Domestic and International AY $2.50
U.S. International Transportation (Arrival/Departure) Tax
Applies to all flights arriving in or departing from the United States, Puerto Rico, or the U.S. Virgin Islands International US $15.10
U.S. Animal and Plant Health Inspection Service (APHIS) Fee
Applies to all flights originating abroad, except Canada, and landing in the United States, Puerto Rico, or the U.S. Virgin Islands International XA $5.00
U.S. Immigration and Naturalization Fee
Applies to international arrivals to the United States, Puerto Rico, or the U.S. Virgin Islands International XY $7.00