Just got back from SA cruise Valparaiso to Buenos Aires 5 weeks ago... Santiago to Valparaiso is about 80 miles -took us about 2 hours by van -there were 3 of us with lots of luggage -cost $100. with tip. Our ride was arranged by our hotel. You can also go much more cheaply with TURBUS- local bus - very safe (all of Santiago is) but getting your luggage to the pick-up location maybe a problem. Taxi is safe but will also cost you $100. If you are arriving at the airport on the day you sail, travel with the cruise pick-up ...my niece did that -get a voucher/schedule of pick-up times from your cruise line - usually cheaper - NCL charged her $50.
A US citizen pays $100. (cash ONLY) for entry into Chile (less for Australian, and Canadians and Mexican, none from other countries - true- it is retaliation for same fee for US Visa app for Chilean nationalities
Hope this is helpful - will be happy to give more info if you wish for more. Our cruise was for 14 days.