A #Regency lady must dress for breakfast, lunch, dinner in, dinner out, more. Cost of that is...?

Opera Dress, left. Promenade Dress, right.
From: 1811 Ackermann's Repository. Google books

     Readers of Regencies love their fashions. In an age marked by the simplicity of line, the simplicity of the look of the cloth, plus the growth of types of cloth available to dressmakers in Great Britain, women regarded their fashion as the key to their success socially.
     Fashion has always signaled status. The decrees of kings (think Louis XIV) and queens (think of Elizabeth I) and various injunctions of parliaments (think sumptuary laws during war times) have limited supply of types of fabrics and inspired protection of home-grown markets.
     But in Britain during the Regency, despite the harassment of a few French frigates and the Barbary pirates, those in Britain enjoyed the variety of fabrics shipped to their shores. Ladies adorned themselves in muslins and silks, satins and laces of all types from many ports of call.
     Here, for your enjoyment, I list a few types of garments and their accompanying costs. My aim is to show you what it might have cost a family to dress their darling girl or cost a lady to dress herself.

(Note well: I take these prices from Cunnington, C. Willett, English Women's Clothing in the Ninetheenth Century. 1990, pp. 34-73. These pages describe women's clothing during 1800-1821. In other words, this is the period of the Napoleonic Wars ending in 1821, the crowning of the Prince Regent in summer of 1821 as George the Fourth, and therefore by strict accounts, the end of the Regency. Also note as Cunnington says, that the costs he found here were ones he could find in advertisements and therefore, they may be the norm, not the most expensive nor least.)

Morning:
Nightgown: cambric muslin, 1+ pounds per yard (2-3 yards necessary)
Morning dress: 15-21 pounds each (ready made)

Undergarments:
Corset: 18+ pounds each
Drawers: cotton, at 3+ pounds each
Pantaloons: worsted, from 14+ pounds each
Petticoat: muslin, 3 pounds
Silk stockings with cotton feet: 7+ pounds a pair

Day gowns, at home:
A gown, muslin, 20+ pounds ready made
shoes: satin or kid, 4+ pounds a pair

Dinner attire, at home:
A gown, merino crepe at 5 pounds per yard
               sarcenet at 7/6 per yard
             
Dinner attire, party, full dress:
Gown:  5-7 pounds per yard  x 3 yards      
Hat/headdress: 4-7+ pounds each
Gloves: long over the elbow, 1+ pound per pair
Shoes: satin, silk, embroidered, 4+ pounds a pair
Cape/redingote: velvet at 7 pounds per yard

And to dress well, other accoutrements are necessary. They would include reticules, fans, parasols, handkerchiefs, and that final bit of embellishment, jewelry.

Now, at minimum of one each of these, we see that our lady's wardrobe costs 123+ pound sterling.
Note my summary here does not address the needs of a young gel making her first Season. Nor does it talk about levels of dress for different types of affairs each of which requires a degree of refinement, all translating to higher costs.
In today's money, how much does that translate to?
If the pound sterling in 1811 is now equal to 70+, then 123 is now equal to:
GBP = 8,622
And that amount in current USD = $13,081.00
With this kind of outlay, one can readily see why conserving fabric was not only a very good practice in all households, but protecting dresses with scarfs and collars and removable cuffs was sound financially. Then too, cutting down dresses to fit not only young girls in the household but also servants was a very practical matter.

Evening dress, left.  Promenade Costume, right.
1812 Ackermann's Repository. Google Books

Descriptions of above fashions, 1812 Ackermann's Repository.
Google books.