Out of MIA I have never paid less than $470 to go to LIM on AA. So look at it like you are getting your ticket to MIA from MCI for $170. The price you are finding is not too bad, IMO. However I think you could price other airlines like Avianca and Taca out of MIA for a lot less (Avianca is sometimes $340 all in, even 1 week before the flight). You can also get to LIM from FLL (Avianca, Spirit) and MCO (Copa) so if you can build a trip on Orbitz to FLL and continue to LIM, you might arrive at a good price.

On another topic, prices intra-Peru on LAN will be considerably higher when the ticket is purchased outside of Peru. Consider using Star Peru. There's also a new airline called Peruvian Airlines (although they are flying old 737-200).