The estimated cost for any file or project is created using the Basic COCOMO algorithmic software cost estimation model. The cost reflected includes design, coding, testing, documentation for both developers and users, equipment, buildings. This can result in a higher estimate then would be expected. Generally consider this the cost of developing the code, and not what it is "worth". It is based on an average salary of $56,000 per year but this value can be changed by the system administrator if the values appear to be too out of expectation.
The calculation itself is very simple.
estimatedCost = estimatedEffort * (averageWage / 12) * 1.8 where estimated effort is calculated by the following
estimatedEffort = 3.2 * Math.pow(linesOfCode / 1000, 1.05). By default the average wage is set to $56,000 (this can be overridden on the setting's page) and the linesOfCode is the number of lines of code in the file ignoring comments and blank lines.