I just watched motorweek the other day and they showed the cut away difference between a premium shock and a regular shock. Both shocks came from the same manufacturer and the difference was startling. First thing that was pointed out was the size an quality of the seals and pistons, the ones on the regular shocks were scary. The regular shock also had poorer welds and a weld seam that ran down the length of the outer piston No such imperfections were found on the premium shock.
If you want shocks that last and are not prone to failure stick with the more expensive shock. In this case money DOES = quality.

Here is the article describing the show....

http://www.mpt.org/motorweek/goss/22010.shtml