Close to none.
>Just because some dude with a fancy name said so doesn’t mean it’s true.
The dude is responsible for tons of what we take for granted. He is also the one who invented the null pointer, so there's that.
I'd take his expert opinion and experience on the matter over anybody referring to him as "a dude with a fancy name".
He didn't sit to calculate the money in damages from it's use - it was more of a figure of speech and a guess ("probably").
But it's very likely that the prodictivity losses from null errors, the consequences for security, program downtime, and so on, could trivially have costed 1 billion dollar in damages over the years - actually much more.
A single null error in one of the space code responsible from bringing down a NASA mission, could easily cost close to a billion itself.
In fact the memory safety industry (e.g. static analyzers and in memory analyzing tools), safety checks for nulls by consultants, and so on, industry easily has have 1 billion in profits over the last 40 years, so there's that...