As the quote is a translation of an original letter, I suspect that the word courtesans might have been in the original.

I don't fully understand all the nuances in the quote. For example, what is the significance of the description of the ladies' dresses?

Why would Prince Starhemberg say "And the ladies, including the princess, had white silk dresses embroidered with golden lace." It is the phrase "including the princess" which intrigues me.

It all made me want to know more about the lifestyle of the times.

Even if the word courtesans wasn't in the original, how do we know it is a mistake by Vincent Meylan? A number of others handle a text such as this before it is published. Christies have professional editors, so if it was a mistake, surely they would have spotted it? Or perhaps whoever keyed in the Lot notes had a minor lapse of concentration.