Fifty miles of good road!

My actual, serious opinion on why Darcy thinks living 50 miles from your family is relatively close while Elizabeth thinks it's far:

Darcy is so profoundly out-of-touch due to wealth, property, influence, his families' status, etc that he truly does not comprehend the complications and expenses of travel for normal people even among the landowning classes. Like, there's all this ink spilled on his status as a gentleman/landowning commoner and what really differentiates a gentleman like Mr Bennet from one like Darcy if anything, and what that would mean in their social context, blah blah. But in pragmatic terms, Darcy's lifestyle and his interests as a landowner have far more in common with the nobility to which he is connected than the typical lifestyles of the gentry.

Darcy talking about 50 miles of good road being nothing in terms of inconvenience and blithely ignoring the costs of either owning or hiring horses, the complications of maintaining a horse if you do own it, the complications around hiring or owning the vehicle drawn by the horse(s), how much more you'd need to pay in services if you don't own the vehicle/horses, what using that vehicle for travel would entail for the workings of the estate or your trade if your family does own it, the cost of stopping along the way, what's lost by the duration of the journey, etc etc. These are things that even fairly well-off landowners like the Bennets would have to deal with in terms of the convenience of travel on "good road" (and also clues us into the prosperity of the Gardiners). These concerns do not even occur to Darcy as problems to consider. This doesn't represent a malicious, personal callousness so much as the genuine obliviousness that arises from extreme socioeconomic inequality. These kinds of problems simply melt away in Darcy's life (read: there are people who make them melt away) and as a result, he truly does not comprehend the impact of prosaic difficulties on the feasibility of something like travel for people like the Lucases or Bennets. The only calculation of convenience that seems to be happening in his head is the effect of distance and road quality on the timing of the journey.

(I think his confusion at people who have family libraries but aren't buying books at this super important literary moment reflects this as well. Books were still quite expensive at the time. He does not appear to grasp that "always buying books" like he does is literally not an option for most people, even in the gentry. He's right about the important literary moment, but "buying things costs money" is a concept that seems not to even enter his calculus.)

My much less serious opinion on why Darcy thinks living 50 miles from your family is "a very easy distance" while Elizabeth thinks it's far:

His landowning family members don't have to think about these problems any more than he does, and if I were Lady Catherine de Bourgh's nephew, I would also consider living 50 mi away from my relatives pretty damn close.

Further diss "angst"

Angst is in scare quotes because it's just silly.

But anyway, I have this argument about how:

1) Historical context is profoundly important to consider when engaging with early modern literature and
2) This lens should not take precedence over the internal elements of a text and
3) Historicist critics should not only attend to the powerful influence of cultural context on early modern literature but also to the effects of critics' own cultural contexts, cultural anxieties etc on their literary analysis and their understanding of the periods they study and
4) It is not actually possible to understand your present "historical moment" and its impact on you with the same perspective you have on an era long past like early modern England because of uhhhh the nature of linear time and
5) You should still try.

The angst is that my first phrasing was "This is not actually possible because of the limitations of the space-time continuum" and then I was like "I don't think this is the project for referencing space-time or even the limitations of linear time lmao" and then I was like "I guess I could just reference 'human' limitations" and then I was like "but does that obscure the matter of chronological perspective that I'm trying to get at" and then I was like "this is a tangent of a tangent about at least trying to put in a modicum of critical thought about how you might be affected by your own culture and preconceptions so you're not a 21st-century version of the 1890s critics whining about the indelicacy of early modern drama..."

Now I kind of want to put the space-time continuum back.