The Operational Costs of a Wall will be less on the Border Patrol since they can now redeploy their forces to hot spots instead of being spread thin, constantly monitoring 2,000 miles, 24/7/365.
For example Border Wall Checkpoints, Airports and Ports of Entry can finally get much needed reinforcements.
With a wall, the cost of dealing with deportees will be less and the entire Justice System should see significant relief from illegal immigrants criminals via
(A) reduced need for prosecution
(B) less overcrowding in jails.
Next, the local police and local justice systems can also better redeploy their resources.