Warren's core claim is verified — Trump did campaign extensively on lowering costs 'on day one,' and prices have generally not fallen as promised. The data is mixed: some items like eggs and gasoline (at end of January) declined temporarily, but broader measures show inflation stuck around 2-3%, major categories like housing and groceries flat, and gas prices surging to $4+ per gallon since the Iran war began. By most measures, Trump hasn't delivered on his signature promise, though the White House disputes this by cherry-picking favorable months and citing items like eggs and some drugs that declined.