How much do border walls cost? Just the facts:

There is a wide cost range for the construction of pedestrian border walls, resulting from factors which include labor (some sections were built by members of the National Guard, while others were built by private contractors); topography; remote vs. urban locations; land purchases and condemnations; materials (wall sections built in the 1990’s used scrap metal, obtained from the military for free, while more recent sections have required the purchase of concrete, steel, etc.); and the design that is being utilized.

In October 2008 the Houston Chronicle reported that “The Army Corps of Engineers estimated that the amount spent for pedestrian fencing has jumped 88 percent since February to $7.5 million per mile. The costs for vehicle barriers have increased 40 percent to $2.8 million per mile, according to the GAO.”
“As border fence lags, costs, controversy rise” by Stewart Powell, Houston Chronicle, October 10, 2008
http://www.chron.com/disp/story.mpl/metropolitan/6052544.html

In January, 2009, the Government Accountability Office (GAO) reported that costs for sections built up to that point ranged from $400,000 to $15.1 million. They also noted that these cost estimates were not independently verified and, “An Independent Auditor's Report on DHS's Fiscal Year 2008 Financial Statements found that CBP did not have adequate policies and procedures in place to properly account for steel purchases and construction of the U.S. border fence in an accurate and timely manner. As a result, for several months throughout the year, CBP’s financial statements did not accurately reflect the construction activity.”
Secure Border Initiative Fence Construction Costs, United States Government Accountability Office, January 29, 2009
http://www.gao.gov/new.items/d09244r.pdf

The GAO’s January 2009 report only included border wall sections that had been completed, not those which were under construction or in various stages of planning.

Sections that were later constructed included the 3.6 miles of pedestrian border wall built through the Otay Mountain Wilderness Area, at a cost of $57.7 million, averaging just over $16 million per mile.
“$57.7-million fence added to an already grueling illegal immigration route” by Richard Marosi, Los Angeles Times, February 15, 2010
http://articles.latimes.com/2010/feb/15/local/la-me-fence15-2010feb15

Also unfinished at the time were the border wall and earthen berm blocking Smuggler’s Gulch, near San Diego, which cost $59 million for 3.5 miles, averaging $16.8 million per mile.
“A Barren Promise at the Border” by Rob Davis, Voice of San Diego, October 22, 2009http://www.voiceofsandiego.org/environment/article_13330282-1245-5e49-bd68-5a10237c9f44.html

According to the GAO it will cost an estimated $75 million per year to maintain border walls. As of mid-May 2009, the fence had been breached more than 3,300 times, with costs to repair each breach averaging $1,300.
Secure Border Initiative: Technology Deployment Delays Persist and the Impact of Border Fencing Has Not Been Assessed, Government Accountability Office, September 2009
http://www.gao.gov/new.items/d09896.pdf

In 2011 the GAO stated that “CBP estimated that the border fencing had a life cycle of 20 years and over these years, a total estimated cost of about $6.5 billion to deploy, operate, and maintain the fencing and other infrastructure. According to CBP, during fiscal year 2010, there were 4,037 documented and repaired breaches of the fencing and CBP spent at least $7.2 million to repair the breaches, or an average of about $1,800 per breach.”
BORDER SECURITY: DHS Progress and Challenges in Securing the U.S. Southwest and Northern Borders, United States Government Accountability Office, March 30, 2011
http://www.gao.gov/new.items/d11508t.pdf

In the spring and summer of 2011, CBP replaced 2.77 miles of existing “landing mat” fence in Nogales, which had suffered numerous breaches, with “bollard” fencing, at a cost of $11.6 million.
“Barrier Rebuilt” by Margaret Regan, Tucson Weekly, June 23, 2011
http://www.tucsonweekly.com/tucson/barrier-rebuilt/Content?oid=3028495

In 2010 the GAO reported that “Since fiscal year 2006, DHS has received about $4.4 billion in appropriations for SBI, including about $2.5 billion for physical fencing and related infrastructure, about $1.5 billion for virtual fencing (e.g., surveillance systems) and related infrastructure (e.g., towers), and about $300 million for program management.”
SECURE BORDER INITIATIVE: DHS Needs to Strengthen Management and Oversight of Its Prime Contractor, United States Government Accountability Office, October, 2010
http://www.gao.gov/new.items/d116.pdf