Differences in prices for the watches you mention, like many timepieces in general, are often based on market value, i.e. what people are willing to pay for them. Surely the collectability and desirability of a watch ultimately determines the market; and as long as there are collectors out there who will pay the price, the prices will be set as they are (although it certainly raised a lot of interesting questions about the watch market when many countries in the world are/were in economic crisis and the prices of watches, which one would expect to go down when people are unable to afford them, are/were still going up! Somebody out there was supporting this market!).
That said, there may be some cost differences in movement production or other aspects of a timepiece. For example, a complicated movement like the Patek CH 27-70 in the 5070 takes more time and work hours to finish and assemble than a simpler movement. This kind of labor does impact cost, and has some effect on the price of a piece as well.
