No one so far has managed to calculate the cost of Monticello with any degree of accuracy. However, the following are several dollar figures that we do know:
Jefferson estimated the value of the house and outbuildings for insurance purposes in 1800 at $6300.
In his accounting of building costs for the period of 4 March 1801 to 4 March 1802 (including workmen's salaries, building materials, and other miscellaneous items), Jefferson noted a total of $2076.29. He calculated his building costs for the following 12-month period to be $3587.92.
Taking the figure of $3587.92, just as an example, and multiplying that by the number of years it took to complete Monticello (28), the total would be $100,461.76. However, there are many variables unaccounted for in this calculation and thus it likely only represents a fraction of the true cost of constructing Monticello. For example, some of the building materials were purchased, and some were made by hand at Monticello; some materials and labor were not paid for with cash but were bartered; and the cost of food, clothing and housing for enslaved workers is not factored into Jefferson's yearly estimates, either. A thorough examination of Jefferson's Memorandum Books might yield a more accurate estimate than the one above, but could probably not ever be considered a definitive figure.
Translating such a figure into today's money adds another layer of complication to this question. There is no easy way to do this, although there are sources that can serve as a guide in making the attempt (see Further Sources below).