For whatever it's worth... I realized that these tires have been on our LR4 for the last 20k miles already. No wear noticeable, no cupping whatsoever.
An expensive tire that can only go for 28k miles is a POS. Factory Contis were trashed on our truck when I bought it at 17kmi - so there you go. Last two sets of Michelin LTX AT2s didn't even have a change to wear out - before the sidewalls cracked so badly that they started leaking air.
It varies a lot by the driving style. I have no experience with the tires you bought (all terrains right?) so they might actually be a decent Goodyear tire. The numbers I threw out were just averages based on what I see on a daily basis. I have seen one set of Goodyears last up to 45k miles on an LR3, but I've also replaced them under warranty for excessive wear causing vibration. Tire maintenance has a lot to do with it as well. The ones that last the longest, in my experience are Continentals and Michelins.