I know we're talking about what the actual law is, but interestingly in that classical example you state, making a product cost 599 is clearly to take advantage of the average person's cognitive weaknesses in thinking of 599 as significantly less than 600.

If they made the prices a round number like 600 as a rule then it would be much more obvious, and probably they would be less likely to make the mistake of making it 100x less than they intended. Bad luck for them.

I wonder how much less they would have made over a year if they made all products that were x.99 be x+1. I'm sure that effect has been measured by these companies at some stage, and that's why they continue to do it.

I don't have a lot of sympathy for any company that makes such a mistake, as the consumers aren't repaid the difference due to their price fiddling, and I'm willing to bet the instances in which a company makes a mistake add up to less than the extra money spent by consumers having their innate biases exploited into paying all those extra cents all day every day.