Short answer: limited used market customers.

If you look at the Midwest there are a lot of small farms that can utilize 2-300hp tractors if priced affordably (think 3-500 acre farms running 875 versatile.)  In some areas of the country the vast majority of the farms run smaller equipment (150hp- tractors with 6 or even 4 row planters, etc) and the 2-300h tractors become impractical for their operations so the used machines end up priced lower due to lower demand, if the price is low enough they can be transported to an area where they are in demand and be competitively priced.  For those large farms the higher depreciation is just another cost of business for the few needing the large equipment.