I don't really think people understand it, it's quite hard to explain and on paper it just sounds like the person is wrong.

The maths for one child for me works out at ~£10k childcare bill without the free childcare vs ~£4000 with free childcare + tax free childcare (for three days a week). Even that doesn't sound too bad but it's the combination of that, the loss of personal allowance and the fact I still have a student loan that means the actual number of how much I have to earn to break even on losing it is something like £30k more than the actual cut off.