6-7-8 speed chains last a lot longer. The 9-10 speed chains are narrower and don't last as long. Also different component groups have different materials for the cogs or the rings. Not always. My 9 speed Dura ace drive train has soft titanium big rear cogs they wore out quickly. The next group down, Ultegra does not have ti big cogs and will last longer. The technical books I have list all the differences between the groups.
The wear is also highly dependent on how you ride, and the enviroment. Rididng in the rain will wear out parts faster for instance. Riding in one gear a lot will wear out that one gear early. Many different factors for wear.
My 7 speed tourig bike has 10,000 miles on the chain, cogs and rings, it's fine.