Indeed they could get a surplus armored vehicle for - FREE.
From the Detroit News:
Warren-based TACOM, the U.S. Army's Tank-automotive and Armaments Command, in June 2004 doled out, free, three armored personnel carriers to the Wayne, Oakland and Macomb County sheriff departments. The departments are required to periodically report back to TACOM on the reliability of the technology used in the vehicle, which can carry up to 13 officers, and perform any needed maintenance.
The Detroit Police Department has not requested a free Army tank (emphasis added), but would likely be a good candidate to receive one, said Don Jarosz, deputy public affairs officer for TACOM. The Army tanks can cost as much as $475,000.