The construction of underground tunnels has become a growth industry for people living in the Gaza Strip:

Gazans are finding an antidote to their growing isolation: digging tunnels under their border with Egypt to smuggle everything from weapons to cigarettes to people.

The tunnels are being created in response to crackdowns by Israel to limit the movement of contraband materials.  The tunnels, which are anywhere from 100 yards to half a mile long, are being used to smuggled various goods into the Gaza Strip from Egypt.

Tunnelers smuggle machine guns, rifles, ammunition, explosive devices, grenade launchers and other munitions. Cigarettes, drugs, gold, automobile parts and people also move through the shafts.

The money involved in the tunneling industry is high.  A person who wishes to be smuggled through the tunnel may pay up to $10,000.  The A.P. has reported that some smugglers have even been able to become millionaires:

Depending on the length, width and sophistication of any given tunnel, they can cost anywhere from $5,000 to $200,000 to build. That cost is the biggest incentive for smugglers to move as much contraband as possible. Profits, too, can be high, with more than a few Gaza millionaires created by smuggling.

One tunneler said the shaft he was digging would take four months to complete and that he expected to earn $12,000 for his efforts — a fortune in impoverished Gaza.