The German 700 MHz auction concluded with a price tag of a billion Euro:
Also auctioned were the 900, 1800, and 1500 MHz bands for a total of over €5 billion ($5.76 b). The 1500 MHz is TDD duplex mode and can be used for supplementary LTE downlink but would require support of this band in new terminals.
* As a side note, the 3G auction in August 2000 raised $46 billion!
For more info: Bundesnetzagentur site