This is a regular economy price and includes a regular sized carry-on bag plus one personal item and standard seat selection. American also has a basic economy fare for $157 round-trip if you want to fly with only a small personal item onboard and don't care where you sit.
Searching Virgin, we found seats departing San Francisco SFO on Tuesday, February 6, returning from Philadelphia PHL on Tuesday, February 13.
Other dates are available for travel on Tuesdays, Wednesdays, and Saturdays from February 6 through March 14. This is part of Alaska/Virgin's One-Day Sale that we mentioned earlier. We're now seeing other airlines match prices along some of the routes.
See our fare details for booking info on the regular economy fare.
Need a room in Philly? Here's what's available for the above dates on Hotelwatchdog.