The cost of different drivers varies dramatically, as does their quality. Shop for efficiency in your driver. Efficiency is rated two ways. The first is half-space reference efficiency, which is stated as a percentage. In both instances, higher numbers are better.
Efficiency is related to several factors.
The mass of the cone will drastically affect efficiency. Tripling the cone mass reduces the acoustic output by one half. Magnet size is also a key factor. Theoretically, doubling the magnet size will double the efficiency. The cross-sectional shape of the wire used on the voice coil also plays an important role.