|V&A, 817-1894 [Source]|
The miniature above, bought by the V&A Museum for £100 from Charles Fairfax Murray in 1894, is valuable both for its intrinsic beauty, and for the fact that it is signed by its illuminator: at the base of the central column is the name "IERONIMUS F[ecit]", making it a touchstone for the style of the artist:
It may be used as the starting point for a consideration of some 19th-century prices and values of illuminated cuttings.
Murray had presumably bought the cutting from Bernard Quaritch within the previous decade; they had offered it for sale for £250 in their catalogue for December 1884 - January 1885 :
This price represented only about a 15% markup, as Quaritch had bought it for £215 at the auction of J[ohn] T[homas] Payne, 10 April 1878, lot 115:
J.T. Payne had formerly -- from about 1825 to 1850 -- been part of the bookselling firm Payne & Foss, which had been a buyer at the Ottley sale, and they had put together the Holford Album of cuttings (as described in this blogpost). When they retired they sold their stock at Sotheby's, 24 June 1850, and eight following days. The Santa Giustina initial was not in that sale, and was presumably part of Payne's personal collection.
It seems very unlikely that Quaritch would have sold the cutting at a loss, so we must assume that Murray paid the full asking price of £250 (or a figure close to it), and certainly could not have got it for less than the £100 that he charged the V&A. But Murray was a generous benefactor to many public institutions, and it therefore seems likely that he was letting the V&A have this initial at less than half of its market value.
It is extremely difficult to convert historic prices into modern ones. In a recent post I tried to suggest what £2,200 was "worth" in 1927 by comparing it to the cost of two brand new limousine cars. There were fewer mass-produced products advertised for sale for £100 or £250 in 1894, making such comparisons more difficult. I very much like the way that Rowan Watson tried to convey a sense of 19th-century values in his Vandals and Enthusiasts 1995 exhibition brochure:
|[Click to enlarge]|
All this makes me very sceptical about the price reputedly paid by W.Y. Ottley for his miniature of The Dormition of the Virgin illuminated by Don Silvestro dei Gherarducci, from a choirbook of Santa Maria degli Angeli, Florence:
|BL, Add. MS 37955A [Source]|
Gustave Waagen, in Works of Art and Artists in England, II, 1838, p. 129, seems to state that Ottley paid £100 for it:
The "l" is potentially ambiguous, however -- could it refer to Tuscan lire (pounds)? [Wikipedia] No: the original edition in German, published the previous year (Kunstwerke und Künstler in England und Paris (1837), p. 401), makes it clear that the the price is in pounds sterling: “Dieses eine Blatt hat aber auch Ottley aus der ersten Hand mit 100 Pfd. Sterl. bezahlt”.
Despite this, I think it is still possible that Waagen wrote "100l" in his notes, meaning lire, and then later mistook it it mean sterling. Another interpretation is that Waagen misunderstood or misremembered Ottley, who may have told him that this leaf was the finest of a group which had cost £100 in total (there were eight cuttings from the same choirbook in the Ottley auction, and he may originally have owned yet more).
If Ottley really did pay £100 for this one cutting, his enthusiasm for it led him to make a bad (financial) misjudgement: when it was sold in his posthumous sale it made only 4 guineas (£4 4s).
 The V&A online description reports that Quaritch also offered it in their Catalogue 332, for November 1880; but I have not been able to consult a copy to verify this.
EDIT, 2 Nov. 2020
Stephen Butler has been in touch to bring my attention to the Measuring Worth website and calculator. Its great strength is that, instead of giving an overly-simplistic single modern value for a historic price, it provides several modern values, calculated in different ways, and helps you to decide which is most appropriate. So, for example, the £100 paid by the V&A in 1894 can be converted to 2019 figures as follows:
If you want to compare the value of a £100 0s 0d Commodity in 1894 there are four choices. In 2019 the relative:
real price of that commodity is £11,470.00
labour value of that commodity is £45,360.00
income value of that commodity is £78,660.00
economic share of that commodity is £148,100.00
For our purposes one of the two middle values is probably most applicable, but the value of the cutting in today's (very different) market for illuminated manuscripts is closest to the highest value.
EDIT, 1 Dec. 2020
Henry Woodhuisen kindly got in touch with me a few weeks ago with an image of Quaritch’s General Catalogue of Books for 1880, in which the cutting was priced £300: