If the error was insignificant in either direction, I would probably ignore it since it would cost me and/or the supplier a lot of money to correct the problem. If the error was more than probably $10-$20 in either direction, I would call them. Shopping locally, where corrections are more or less instant, I would react to an error larger than $1 in either direction. Possibly all the way down to the smallest possible error in the local currency.
If someone gives me $100 I would be happy. If someone accidentally gives me $100 I wouldn't be able to enjoy it. If someone takes $100 from me, I would be angry. If someone takes $5 from me, I would be irritated but probably ignore it.
In some situations, it can be quite hard/expensive to bother. What to do if buying something in a shop, and the price is $10 off. I don't notice the error until I'm home, and it costs more than $10 to drive back to the store? If they charged me too much or supplied the wrong article (or a broken one), then by local law I can also require them to pay my costs for correcting the error. If they charged me too little, I would have to pay the extra costs for solving the problem unless they gave me a better product than I requested. I don't like to correct errors if one part would have to pay as much just for correcting the error. But I may call the supplier and telling them that they shipped a $10 more/less expensive item but that I'm not interested in a one-hour car drive to get it switched. At least, that would allow them to correct any pricing/marking errors they have so the same thing doesn't affect other customers too.