If passengers return on the same day, Monday to Friday, the fare is a whopping $720.
If a traveler spends one or two nights in Boston, the fare drops to $520 round-trip.
Fares are cheaper on Saturday - $320 to fly to Boston on Thursday, Feb. 23, for example, and return to Philadelphia on Saturday, Feb. 25. But it costs $520 to return Friday, Feb. 24.
The key is to fly on, or stay over, a Saturday. Not what most business travelers do.
"We are returning to the days of 10 years ago, when flying Philly to Boston was over $1 a mile. This is simply gouging," said Kevin Mitchell, chairman of the Business Travel Coalition in Radnor. "It's taking advantage of business travelers, who really don't have another option to get from Boston to Philly, or Philly to Boston, efficiently."
Jeffrey Erlbaum, owner of ETA Travel in West Conshohocken, said that, when Southwest flew the route, same-day fares were about $250. "Now it's in the $700 range if you want to go in the morning and come back that same night."
Erlbaum said more Boston-bound clients were opting to take the train. "The Amtrak ticket is $147 round-trip."
When airlines have a monopoly, they stick it to the business traveler, who they figure can expense it, said George Hobica, founder of the travel comparison website AirfareWatchdog.com.
Philadelphia is not alone, he said. Fares have risen in other cities where AirTran Airways, now part of Southwest Airlines, has dropped service.
"Consolidation leads to higher airfares. Two things happen: People will drive when possible on shorter distances, because they are not going to pay those fares," Hobica said.
"And sometimes, another airline will go in - Allegiant Airlines, Spirit Airlines, JetBlue Airways. Some of the discount airlines will pick up the pieces."
If fares get too high, it will invite new competition, said William Swelbar, research engineer at the Massachusetts Institute of Technology's International Center for Air Transportation.
"It's a fascinating case study that Southwest was not able to make a go of it and that they vacated Providence and Manchester, too, which were their secondary doors into the Boston metro market," Swelbar said.
"It speaks loudly to the presence that US Airways has in Philadelphia, and its frequent-flier base. If Southwest can't make a go of it, it's hard to imagine who might."
Southwest began the Philadelphia-Boston route in June 2010, with an introductory one-way fare of $59.
US Airways immediately matched Southwest's fares.
When US Airways had a monopoly before to Boston, 278 air miles from Philadelphia, fares were as high as $550 one-way for a nonstop coach seat, or $1,100 round-trip.
Southwest spokesman Chris Mainz said in September that the Boston route "just hasn't performed the way that we would have liked."
US Airways can make a profit on routes to Pittsburgh and Boston, where Southwest could not, because Philadelphia is a US Airways hub with 429 daily flights. The carrier, based in Tempe, Ariz., takes passengers from here on to many other destinations and does not depend only on traffic that begins and ends their journeys in those cities.
AirTran stopped flying between Philadelphia and Boston in 2007. In August 2009, Delta Air Lines also dropped the route. US Airways has 15 daily weekday flights to Boston.
JetBlue spokesman Mateo Lleras said JetBlue planners were looking at the Philadelphia-Boston route along with "many other options" after Southwest and AirTran pulled back from a number of cities. "Our network planning team is studying a great number of alternatives, but nothing definitive at this point."
Contact staff writer Linda Loyd
at 215-854-2831 or email@example.com.