"That's one of the reasons why, even if you loved everything about your health insurance, there was a need to go down a path to lowering costs," she said.
"If we're talking about fiscal stability, the Affordable Care Act is an act of fiscal stability."
The CBO will release its new cost projections for the law during the week of July 23.
Pelosi commented on the law's costs while discussing a GOP spending bill that includes deep cuts to labor, health and education programs.
The measure cleared an appropriations subcommittee on Wednesday by a vote of 8-6.
"What they marked up is, in my view, an immorality," Pelosi said.
Later, she tweeted: "GOP pushing destructive bill that will strip $ from family planning, prohibit $ for Planned Parenthood + repeal Obamacare."