High-end balls typically have new, high-tech cores. The core might me made of different density pieces or have an unusual shape. That adds to the manufacturing cost of the ball. Additionally, that high-tech (usually asymmetric) core will allow for more variety in ball reaction due to layout differences. So the high-end ball might be more versatile with regard to layouts.
Next, high-end balls typically have newer coverstocks. The money that has been put into R&D for the cover has not yet been recouped through ball sales, and so more is charged for the cover. Additives might be included that are more expensive as well. The Soaker additive in Dynothane's and 900Global's high-end balls is supposedly more expensive, which is why we are unlikely to see any mid-priced Soaker-covered balls.
Mid-priced balls tend to have simpler, less expensive cores. Or cores that have been around for a while (Columbia and Ebonite have been using many of the same cores in their mid-priced equipment for years). Covers are usually older technology that has stood the test of time (PK18, Superflex, Accutread, Trimax, Big Bang).
That's not to say that high-end balls are better. PK18 and Superflex are fantastic covers that hold up well, take surface adjustments easily. If you can't get 300+ games on a ball with that cover, you're doing something wrong. The cores hit just as hard as anything else. Mid-priced balls and entry-level balls can more than hold their own with high-tech, super-charged top-of-the-line equipment.
The only caveat with high-end equipment, the strong asymmetric stuff in particular, is that they can be very sensitive to release changes. If you can't be consistent with your release, you might get one great shot and one lousy shot with a strong asymmetric. A simple, symmetric-cored ball (high-end or not) will be more consistent with an inconsistent release.
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