So, you’re donating your Nike gear to charity....you will need to determine Fair Market Value.
Problems in Determining Fair Market Value
There are a number of problems in determining the FMV of donated property.
Unusual Market Conditions
The sale price of the property itself in an arm's-length transaction in an open market is often the best evidence of its value. When you rely on sales of comparable property, the sales must have been made in an open market. If those sales were made in a market that was artificially supported or stimulated so as not to be truly representative, the prices at which the sales were made will not indicate the FMV.
For example, liquidation sale prices usually do not indicate the FMV. Also, sales of stock under unusual circumstances, such as sales of small lots, forced sales, and sales in a restricted market, may not represent the FMV.
Selection of Comparable Sales
Using sales of comparable property is an important method for determining the FMV of donated property. However, the amount of weight given to a sale depends on the degree of similarity between the comparable and the donated properties. The degree of similarity must be close enough so that this selling price would have been given consideration by reasonably well-informed buyers or sellers of the property.
Click here for more information: https://www.irs.gov/publications/p561#idm140501112136960