OK - OK
I know the trains actually terminate in MIA and NYP. I was just trying to illustrate a point. A train running through 5 states from JAX to ALX [or DC] (were it to terminate in both places) would not be thought of as anything less than "Long Distance" by any normal person ... but the 750 rule could make it otherwise.
I hope that clears up the confusion ...
Gosh! I have to remember that even when one is warned about being pedantic people can really go off the deep end arguing a point. I was surprised by the $hitshow that followed my more or less non serious leg pulling comment, where I even mentioned the Alexandria thing.
But more seriously as I mentioned earlier, the 750 mile thing is a rather low quality proxy for the desire to have local and regional service funded predominantly from local or regional funds. It also came as a desire to protect the funding from long distance service from redirected spending on short/medium distance trains ( complaint that persists viz-a-viz the NEC still). To some extent the fact that everyone is up in arms about 750 miles suggest that that mission may have succeeded., but the method used is in dispute. Now stating and illustrating the obvious faults with it a zillion times is neither going to fix the fault nor cause anyone to get more excited about it. The whole funding formulae was a mess before this and it is a new form of mess now.
I suspect in some quarters, part of the motivation of the 750 miles was also to get the likes of NY State to pay for their Regional service which until then was grandfathered as federal responsibility, except the 403b Adirondack. Interestingly, the folks who were complaining the most about it also had a few grandfathered regional trains, but they had been investing local money for adding service, unlike New York, which even now has added no new service, and is yet to get food service back in its own funded trains between NYP and ALB. In some sense it was to an extent an attempt by regional service "have nots" to get regional service "haves" to contribute a bit more local fund. In some sense the same struggle, reasonably or otherwise, continue regarding the NEC.
The problem with this approach is that you forego any revenue that might be obtained from passengers riding between Boston and stops in New Hampshire, while retaining 100% of the costs. This increases the losses, which increases the subsidy requirement that Maine must pay.
So you will almost always have to keep it as-is, which really eliminates the practicality of using that as a way to get intermediate states to pay for it.
In colloquial language it is very nicely characterized as "cutting your nose to spite your face".
The fact of the matter is that in principle we do run LD trains through lots of net receiver states, so in some sense they do not pay for them either. But we do so for the sake of maintaining connectivity and providing meaningful service. People who board in NH do bring certain amount of economic activity to the places that they visit in Maine and Massachusetts too, so it is not entirely a loss, and as Trog mentioned, it does bring in revenue that would otherwise be foregone while the costs pretty much remain the same.