Why does it cost $1 billion for the state to spend this year on incarcerating illegal aliens?

Why does it cost $1 billion for the state to spend this year on incarcerating illegal aliens ? I was told everybody was here to work and only wanted a better life, so why is their such a huge incarcerating of illegal aliens at 1 billion per year and if we add the rest of the states, does this dwindle into 300 billion illegals are said to pay in taxes ? The proposal also includes $330 million to help states pay for jailing illegal immigrants. The money has long been a priority for California officials, who argue that local and state taxpayers should not have to bear the burden of Washington's failure to control U.S. borders. California's expected $90-million share would represent a fraction of the nearly $1 billion the state probably will spend this year on incarcerating illegal immigrants.a href="http://latimesblogs.latimes.com/lanow/2010/02/california-gets-help-paying-for-jailed-illegal-immigrants-in-obamas-budget.html" rel="nofollow"http://latimesblogs.latimes.com/lanow/20…/a