No idea as to how they are on fuel surcharges (which is the only variable in the cost, the real taxes are the same for all airlines), however LAN is hopeless for ticketing and unless you know someone at LAN you will never be able to actually get the ticket issued. It will take 100x the effort of dealing with AA. I tried once, and after the first hour hadn't managed to get LAN to understand that I was trying to buy a OWE product; gave up at that point. Perhaps there is a RTW specialist person at LAN, but I never found them.