As a point of reference, the BOM for last year's Burning Man setup can be found at the bottom of this page: http://gnuradio.org/redmine/wiki/gnuradio/OpenBTSBM2009RF

The default hardware for OpenBTS is the USRP, not the USRP2. The USRP + 2 RFX 900 daughtercards set me back about $1400.

OpenBTS units like these use Intel Atom SBC boards, which retail for <$100: http://www.intel.com/products/desktop/motherboards/d945gclf/...

The bare hardware cost is less than $5K, but perhaps the $10K price quoted in the article includes the tower, rigging, cables, power source, enclosure, Wi-Fi backhaul, etc., not to mention a nice profit margin.

Incidentally, there are some gnarly GSM patent licensing issues that are discussed in the January 2009 entries on the OpenBTS blog.