That routing is, unfortunately, a limitation of the century+ old Pennsylvania Railroad. We'll never see a maglev from center city PHL directly down to AC via the 42 freeway and AC Expressway.
In fact, Amtrak used to run that route many years ago. Not profitable even for a quasi government operated entity. You don't see NJTransit rail servicing any other PA stations either. This was the result of some kind of deal made when Amtrak dropped the route years back.
I'll say it again - most people flying AA on this kind of route with a PHL - ACY bus connection will not have AC as their destination. They will be AC area customers who originated their trip there and opt to do this if they can't get/pay for a ride to PHL or want to park their car. Given that AA hasn't served AC (ever?), this may be a brief experiment.
That'd be a narrow market but maybe.
Anyways, I'll be interested to see how AA prices the tickets to ACY via PHL bus.
Many times, AA offers fares to ABE less than PHL. I've seen RDU-CLT-ABE as an example, less expensive than any RDU-PHL nonstop or connect via CLT as it appears to have a premium that PHL is a hub. But that might be the case on random one-ways here and there but just something that I noticed.
if AA prices a premium to use the PHL-ACY bus then it will be unpopular.
On how parking affects, it is scarcer at PHL as the economy parking lot at PHL will not re-open:
https://www.inquirer.com/business/ph...-20211104.html
I think the typical rate at an offsite parking is in between $20-25/day, at least from checking a few ones, The Parking Spot and Wally Parking.
BWI still has low parking costs, $12 a day in a garage, but it's a bit too far for most, but still has a lot of nonstops and flights.