Earlier in the thread you suggested that it's hard to justify ncdu using 60MB while it takes only 3.5MB to store 400K * 8 bytes numbers. The number you came up with is just silly and overlooks actual complexity of the problem.
Given that you are making an implicit judgement about the other program, don't be sloppy with your estimates.
Given that you are making an implicit judgement about the other program, don't be sloppy with your estimates.