Beneatha hyperbolically claims that Mama can buy a rocket ship with the insurance payout for all she cares:
That money belongs to Mama, Walter, and it’s for her to decide how she wants to use it. I don’t care if she wants to buy a house or a rocket ship or just nail it up somewhere and look at it. It’s hers. Not ours—hers.
While one would presumably need a little more money than is included in the insurance payout to buy a rocket ship, the hyperbolic claim Beneatha makes underscores her broader point: that it is Mama’s money to spend on whatever she wants, and that Beneatha does not care what that entails. The hyperbole Beneatha uses emphasizes the life-changing amount of money that is 10,000 dollars, which is a ticket to another world for the Youngers—making the insurance payout not far off from a rocket ship.
At the same time, the Younger family can't help but reflect on what they each individually could do with that amount of money. It generates the central conflict of the play and, directly or indirectly, results in each character voicing their dreams. Thus, while Beneatha is being hyperbolic, the insurance payout is in fact life-changing for the entire Younger family, not just Mama.