There are several reasons why arresting cables aren't used on land:
As Manfred noted, the stress that gets put onto a plane during landing is incredible. According to HowStuffWorks "How Aircraft Carriers Work", its not unusual for an aircraft to hit the deck at around 150 mps or about 67 mps. Since they have less than 500 feet of runway (~150 meters), they must decelerate at an incredible speed to a standstill in about 2 seconds. That equates to about 3.5 G's! In addition, Navy pilot's are taught to push the throttle to max upon hitting the deck so that if they miss one of the 4 cables, they can still have enough speed to take off and try again. This may now happen automatically as Chris S noted, I'm not certain. This means that the aircraft has to undergo even more stress. Navy planes must hit the deck so hard that its often compared to a controlled crash instead of landing and aircraft frames must be structurally modified to endure that type of stress.
According to Tom Clancy's, Carrier: A Guided tour of an Aircraft Carrier, it is extremely difficult to catch the wires. Its so difficult that Navy Pilots are often ranked on how often they hit the 2nd wire (considered to be the best).
As Manfred noted above, the machinery to slow an aircraft is not trivial. While I'm not familiar of the routine replacement rate for these cables, I would imagine that it would be something else that would have to be monitored. The cable is actually attached to a large machine which provides the cable with some give. I can't imagine that they would be cheap, but I'm not familiar with the exact machinery myself.