I'd have thought 60g was within the manufacturing tolerance. So probably a phycological effect as much as anything.
No, no and no.
Whether 60g is a manufacturing tolerance for a top of the line helmet I do not know. I wouldn't think it is, to be honest. I see one place quoting the helmet weighs 1.2 kg. A 60g variance would be 5%, which I assume would be fine for a run of the mill product, but not for an F1 helmet.
However, if I was an F1 driver, I'd tell the manufacturer to send me the lightest helmets + I'd weigh them and use the lighter ones in races and the heavier ones in testing.
Moreover, even if 60g is a manufacturing tolerance, then 60g saved is still 60g saved. I don't see how manufacturing tolerance has any effect on this. Example:
a) Helmet weighs 1200 grams. If I add 60 grams to it, it weighs 1260 grams.
b) Helmet weighs 1260 grams. If I add 60 grams to it, it weighs 1320 grams.
So adding weight adds weight. Not adding weight prevents weight from being added.
Lastly, I think the gain in laptime of 0.002 seconds is absolutely negligible. It could once in a 10 year F1 career mean you make up a place on the starting grid. Although, Schumacher, Villeneuve and Frentzen would appreciate it. Nevertheless, I think the saved weight comes in handy at places like Interlagos where the driver's necks are strained to the limit and a 5% reduction in weight could be appreciated as it will in the end allow a driver to be slightly less fatigued and mean they can be more precise and I'd imagine a saving of one inaccuracy, meaning 0.1 seconds can easily occur during a race.