Data point on web site differences.

BOG-LIM rtn on Peru site $448. US site is $448
BOG-LIM rtn on Colombia site $331.
(All had the Colombia exit tax included)
This is replicated on ITA: using BOG as sales city gives same difference as LIM as sales city. (so tip, do this change when searching ITA)

As well, certain days had different fares differences. i.e. Cheapest fare available on Colombia site on certain day but for the next day on Peru site.