Slaves prices can be found to vary on sale notices, bills of sale, etc., depending upon age, sex, skills, health, etc., etc.
I have seen children sold for as low as $2.50 or $3.00, and adults for anywhere from $275 to over $1800.
Trying to convert modern U.S. Dollars to "Civil War" dollars seems to be complicated, and different conversion tables like to give a wide range of values.
IMHO, I like to put it into perspective by thinking that an unskilled laborer earned about $1.00 a day versus the $2.00 plus a day earned by a skilled craftsman. (Without getting into 12-16 hour work days, six days a week, etc., etc., ). And then thinking if I were a skilled craftsman making $12 a week, or roughly $50 a month... Or a working class lad making roughly $25 a month...
In gleichem Schritt und Tritt, Curt Schmidt
Not a real Civil War reenactor, I only portray one on boards and fora.
I do not portray a Civil War soldier, I merely interpret one.