I
asked about this on the S. America forum, and they referred me a couple of bus companies that will get you from Lima to Santiago for $65. These companies offer the new luxury buses that I assume are geared towards tourists and wealthier locals.
$27, 18 hours: Lima-Tacna:
http://www.turifax.com/pau1eng.htm
Cab across border
$40, 30 hours (not 6, as was pointed out): Arica-Santiago:
http://www.turbus.com or
http://www.pullman.cl
Which means you could probably do it for $40 on local buses.
Someone also mentioned that you can
avoid the $100 Chile reciprocity fee by crossing overland into Chile.
For me, this is great info because I can fly to LIM (or even GYE) instead of EZE or SCL and save a load of cash. What is it about flying into EZE or SCL that makes it so damn prohibitively expensive?!