Economic growth is the key to resolving the paradox you highlight of his seeming wealth then being inflation adjusted to only modestly high net worth today.
Using Maddison's estimate for UK per capita GDP in 1820, suggests that the average UK resident generates more than 10.7x as much wealth now than back then.
Of course, all these comparisons are fanciful and dependent on the utility one assigns to various things. In terms of the number of servants he could employ, a man of Darcy's wealth far outpaces all but the wealthiest in the first world whereas in terms of his ability to travel to Rome expeditiously, he can't measure up to a nearly broke student.
Yeah, the wealth generation statistic is interesting. I think a related way to think of why amounts of wealth that seem nominally not that extreme by today's standards were extreme hundreds of years ago is that there was much less you could spend that wealth on. People just didn't have the capacity to accumulate nor spend money to buy things and services at the same rates.
So viewing money as tokens of value, there was just less 'value' around full stop. So having much less of it still made you relatively extremely wealthy.
You could always spend wealth on land, building a manor, hiring staff to maintain the land/manor, arts, crafts, travel, even science.
Also, how much would Darcy pay for an electricity generator, an old CRT television with a PSX and all the PSX games ever made? That makes comparisons in discretionary spending difficult.
But comparing basic spending could be doable. It is, of course, easier to compare such spending for a median person than for an outlier.
Yeah it's extremely interesting to think about - it's all a system and when you think you could just spend more money on whatever was available (building a bigger house, horses, arts, hiring staff) you also have to consider that there would have been much tighter upper limits on all of these. The labour market was extremely illiquid, and smaller, and economies of trade and skills were much more localised than today.
Doubtless you could simply waste your money pretty much without limits (pay more unqualified people to do a bad job at building your house, for example) but it would have been much more limited in terms of how you could usefully deploy your wealth, just because there was much less of everything available.
Might have your characters mixed up? Darcy has plenty of land, Bingly wants something fitting his standing as a man of means. However, many rich/aristocratic families were prevented from selling their real estate interests, and could only access the derived profits. This naturally reduced the availability of land.
Using Maddison's estimate for UK per capita GDP in 1820, suggests that the average UK resident generates more than 10.7x as much wealth now than back then.
Of course, all these comparisons are fanciful and dependent on the utility one assigns to various things. In terms of the number of servants he could employ, a man of Darcy's wealth far outpaces all but the wealthiest in the first world whereas in terms of his ability to travel to Rome expeditiously, he can't measure up to a nearly broke student.