If you mean the monetary vlaue it is a difficult question as an expert estimation would only be made if a Vermeer-painting would be sold (e.g. at an auction). The last sale of a Vermeer, the small ‘Young Woman Seated at the Virginals’ (at least now attributed to Vermeer by a team of experts) took place in 2004 at Sotheby’s and fetched the sum of £16.2 million (c. $30 million).

The sums of earlier sales of Vermeer-paintings are listed in Arthur Wheelock (ed.): Johannes Vermeer (exhibition catalogue), Zwolle 1995/96 resp. in Walter Liedtke: Vermeer. The Complete Paintings, 2008, as far as they are known from archival material.

It seems out of question among Dutch 17th century painting experts, that the Procuress in Boston is the original by Dirck van Baburen (also as it is signed), and a comparison only of the images of the actual 3 versions (despite their different quality) proves this statement, as both the Amsterdam copy and this newly appearing one from the Courtauld Institute are far broader even in the rendering of flesh tones.

Furthermore, it seems likely that Maria Thins, Vermeer’s patrician mother-in-law, have owned the original Van Baburen, as presumed in the Provenance/Ownership History from the Boston museum’s website. The painting dates from 1622, and quite such a picture (“A painting of a procuress pointing in the hand”) is listed in an inventory of 1641 documenting the marital property after Maria Thins’ divorce from her husband Reynier Bolnes. Maria Thins had probably some connection to the Utrecht Caravaggists (of whose Dirck van Baburen was one of the most prominent representatives) via her distant relative Abraham Bloemaert, the great Mannerist painter of Utrecht.

The Rijksmuseum Amsterdam dates its copy of the Procuress 1675 to c. 1725, so it is a rather late copy probably made from an unknown artist of the (closer or wider) Baburen-circle, and it is unlikely that either this or the Courtauld copy once was in the Maria Thins-estate.
As the two copies from the Rijksmuseum and the Courtauld Institute seem to show the same broadness in execution (as far as possible to judge from the poor quality of the Courtauld-image) both might have been done by the same artist as copying from the masters was usual practice in that time.

What is beyond my comprehension is the long-lasting believe again of art-historical experts that the Courtauld painting might have been a fake by Han van Meegeren. Didn’t they have learned from the mortifying cases even of his Vermeer-fakes?? Only a discrete knowledge of Van Meegeren’s style of flat, ghostlike figures would have been sufficient to disqualify him from any ‘authorship’, moreover, as he not copied one-to-one (as done here with the copies in question) but rather painted ‘in the style’ of Vermeer or Frans Hals (and, of course, in about the same painting technique).

A further queer thing at the end: Just read what uninformed journalists, nothing but greedy for sensational stories, have made of this new puzzling case!
http://www.thisislondon.co.uk/standard/article-23749455-seeing-the-light-a-courtauld-fake-which-may-be-a-vermeer.do

They should better start thinking before writing!

ARech