That is because the 28% cap apparently refers to a bracket of taxable income, which includes itemized deductions.

WSJ: Tax Report: Is Taxing Health Plans Next?

The marginal tax rate is the rate paid on the taxable income, in the highest tax bracket.

FORBES: Countries With The Highest And Lowest Taxes

While the write-off would make no difference to a tax-exempt investor, a taxable investor in the 30% tax bracket would get an after-tax income stream comparable to another REIT yielding 7.14%, a substantial difference.

FORBES: Norfolk Southern v. Power REIT: Worst Case is Much Better Than Nothing