The charge referred to above is a "reciprocal fee" - it's what the US charges Chileans for a visa, so Chile figures it ought to work both ways. There are similar charges, for the same reason, for Canadians and Australians. Must be paid in cash of the country in question before you get to passport control. Takes 30 seconds, zero hassle.

If you're going as a family, keep in mind that the charge is per person so be sure to have enough cash on hand for everyone.

Once you pay, they staple a small certificate to the last page of your passport. It's valid for as long as the passport is.