New Jersey spends an average of $17,700 a year per student - documented or not - through grade 12, Christie said.
"The question is: Do we want to maximize that investment through giving them nothing more than an opportunity?" Christie said. "Even if you're coldhearted about this, you can agree with the common sense of the economics. An investment made should be an investment maximized."
While the bill is already law, Christie signed it a second time Tuesday, flanked by Hispanic leaders and Democratic lawmakers during the ceremonial event.
Christie had drawn accusations of flip-flopping after he refused to sign an earlier version of the legislation that would have made undocumented immigrants eligible for state financial aid. The students cannot receive federal aid, such as Pell grants.
The governor, who won 51 percent of the Hispanic vote in November's election, had told Latino groups before the election that he supported in-state tuition. When Christie later announced that he would not sign the bill working its way through the Legislature, opponents accused him of trying to avoid a controversial subject before an anticipated presidential bid.
Christie denied changing his position but said he did not support giving state aid to students who were not citizens. He negotiated with Senate President Stephen Sweeney (D., Gloucester), one of the bill's sponsors, to strike the aid from the bill.
"Sometimes people react hysterically when people disagree in public," Christie said Tuesday. He said he and Sweeney - who was in Washington during the event - "committed to each other that we had to find a way to make this happen."
By finding compromise, "we also set an example of optimism," Christie said. "Unlike what happens in Washington, the government can actually work for you."
Addressing students, Christie said, "You are an inspiration to us because in you we see all that the future of our country can be. . . . We see the infinite possibilities of the human spirit."
Democrats who spoke before Christie also touted the importance of compromise. Sen. Brian Stack (D., Hudson), who is also Union City's mayor and who endorsed Christie in his reelection bid, said Christie had "shown not just New Jersey, but this country what it takes." Also on stage were Sen. Teresa Ruiz (D., Essex) and Assembly Speaker-elect Vincent Prieto (D., Hudson), cosponsors of the bill.
While "everything is not achievable at this time," Prieto said, "this is a fantastic start."
Under the law, which officials said took effect this month, undocumented immigrants must attend three years of high school in New Jersey and graduate there or receive the equivalent of a high school diploma to be eligible for in-state tuition.
Advocates say it is unclear how many immigrants might benefit from the new law. The population is difficult to track, and not all who are eligible would attend college.
According to New Jersey Policy Perspective, a left-leaning think tank, 28,500 immigrants in New Jersey were immediately eligible for the federal Deferred Action for Childhood Arrivals policy enacted in 2012, giving temporary relief from deportation to certain young undocumented immigrants and allowing them to receive driver's licenses and work permits.
New Jersey is now among 15 states that allow undocumented immigrants to pay in-state tuition rates, according to the National Conference of State Legislatures. Two states - Oklahoma and Wisconsin - previously allowed the practice but ended it, and several states, including Arizona, Georgia, and South Carolina, have banned it, according to the national conference.
Speaking in support of New Jersey's new law Tuesday were Carlos Medina, chairman of the Statewide Hispanic Chamber of Commerce, and Martin Perez, a Christie ally and president of the Latino Leadership Alliance of New Jersey.
By working together to pass the bill in New Jersey, "we are sending a message to the whole country," Perez said.