Thanks - I'm not clear it actually makes a difference in the filing (maybe the IRS just doesn't care about the method reported for publicly traded securities), but TurboTax's own instructions suggest that "comparative sales" is the wrong choice. If I click the question mark next to "Valuation method" in the "Step-by-Step" process, TurboTax's guidance says:
The valuation method is whatever is used to determine fair market value. For stocks, that usually the average share price.
(Of course, they mean "that is usually.")
