"When selling a rental property, you have to pay taxes on the recapture of the depreciation that you should have claimed, even if you never actually claimed it.  Yes, that's as bad as it sounds"

Here is the fact: If a taxpayer did not claim deprecation in prior years. At the year when he sells his property, prior year accumulated depreciation amount is entered by "0". so related recapture deprecation amount is also 0 instead putting a positive number there. 

It is just a simple math,

capital gain =selling price- buying price. Or 

capital gain= selling price-accumulated deprecation + recapture deprection -buying price