Most of the top pro-line brands such as Adams, Callaway, Nike, Ping, Titleist and TaylorMade, offer drivers with adjustable hosels that let you change the loft and, in some cases, the face position, using a supplied wrench. Titleist offers this option with their 913 fairway woods and hybrids. The manufacturers offer a wide range of shafts fitted with tips that can be interchanged with their respective drivers, which lets you play with your favorite club without sacrificing performance on windy days, long or short courses or other conditions where one shaft/loft combination would work better than another. Phil Mickelson has played with two drivers (or no driver), but most golfers get settled with one driver and want to use it everywhere they play. This is also the case with a favorite 3-wood or even hybrid. At Klees Golf Shop we often have many of the shaft options each manufacturer offers, and you can try them all in a club fitting or take a few out to the driving range.
The $400 price point in these new drivers includes the kind of fitting and flexibility unavailable in a lesser priced club. Whether you take advantage of these features is up to you, but you pay for them. It only makes sense to see for yourself what shaft and fitting options are offered and what combinations suit your game, wherever it is played.