Conditions for mileagerunners are bad these days, but I still refuse to consider a $288 transcon "mileage run forum worthy." Of course, at the rate prices are rising, it soon might be.

What seems to have happened this summer is that the airlines are levying an automatic surcharge for most summer travel days, eliminating everything near the $200 transcon level. That surcharge seems to expire in late August, which is when you found this fare. The cheapest late August PHL transcon seems to be to SAN on CO, which you can buy in the $230s.