Once in Mexico, these weapons are worth at least double those prices, and in some cases as much as triple or more,

With over 2,100 deaths between January and October 2007 related to drug trafficking and the use of weapons purchased in the US, Mexico pins its hopes on the future success of the Merida Initiative to combat drug and gun trafficking.Mexican authorities now estimate that during the administration of former Mexican president Vicente Fox (2000 to 2006), some 2,000 guns per day entered Mexico. That works out to about 1.4 guns per minute. During that same period, the Fox administration seized 8,088 guns of the estimated 4,380,000 that entered the country, representing 0.18 percent of all the arms illegally smuggled into Mexico over six years, according to Mexican daily La Reforma. These salesmen and strawmen are the primary sources of illegal weapons flowing south, which they sell or hand off to gun traffickers who generally group the shipments at specific border crossings. Once in Mexico, weapons smugglers are set to make thousands on their merchandise.
"A used AK-47 may sell for around [US$] 400 and up," Litzman told ISN Security Watch. He added that an AR-15 could sell for US$800 to US$2,000, depending on the model and age of the weapon as well as other options such as the scope, stock or trigger guard.
Once in Mexico, these weapons are worth at least double those prices, and in some cases as much as triple or more, according to the ATF. One AK-47 purchased in Arizona for US$500 might go for as much as US$1,500 or more once it crosses the border.
At border crossings, Mexican customs agents are in the best position to detect smuggled weapons, but their situation is a difficult one. Many are given the well known choice of plata o plomo. "take the bribe or take a bullet." This is the clear message Mexican organized crime groups send those who patrol the Mexican side of border crossings, known as "plazas."
In February this year, a Mexican customs agent stopped a truck in Matamoros, a town across the border from Brownsville, Texas, under the control of Mexico's Gulf Cartel. The agent seized a load of weapons including 17 grenades, 18 rifles and 17 pistols. The next day he was killed with an AK-47.
The Mexican military, since its deployment to troubled spots in central and northern Mexico, has had some success seizing smuggled weapons. On 13 October, soldiers seized a weapons cache in central Tamaulipas state, located on the Mexico-Texas border. The public list of seized weapons included 11 AK-47 rifles, 13 AR-15 rifles and over 700 clips of ammunition. The Mexican daily El Milenio reported that one grenade launcher, powerful enough to destroy a tank, was also recovered.
But a review of Mexican reports reveals that such large seizures are limited. Finding weapons left at the scene of a crime is more common. Mexican officials have opined that hit men leave the weapons behind for two reasons: They do not want to be found with the weapons in the future and it is easy for them to obtain more.