Surprised Philadelphia ranks so cheap; I was under the impression it had prices similar to other New England cities like Boston or DC.

Like every other BS "It costs this much" story, it depends on what specific location you're looking at and how much you want to not deal with crime. In Philadelphia you'll find three homes selling for $450k, $800k, and $1.2m on the same gentrified block in Northern Liberties, and people will walk past you on the sidewalk saying "I grew up here, but I can't afford to live here anymore", and then there's https://en.wikipedia.org/wiki/Philadelphia_Badlands and https://en.wikipedia.org/wiki/Crime_in_Philadelphia

In the DC area it’s super duper expensive compared to Philly and has pulled further from it as Philly hasn’t boomed as much. In comparison, Seattle used to be a lot closer to Philly in overall cost of living back in the mid 2000s (still more expensive than Philly) but in more recent years has definitely surpassed the DC area in cost of living. However, Los Angeles was higher than both and has steadily gotten more expensive and accelerated substantially less.