Construction

Besides the outer covering, the other important components of a soccer ball are the lining, the bladder, and the stitching.

Lining:  Material thickness plays a vital part in the quality of hand-sewn soccer balls.
Multiple layers of lining are placed between the cover and the bladder. These layers are composed of polyester and/or cotton bonded together to give the ball strength, structure and bounce.
Professional soccer balls usually have four or more layers of lining.

Bladder:
 Latex and Butyl are the most common materials used in the construction of soccer ball bladders.   Latex bladders provide a soft contact and a good bounce, but are not good at air retention since micro pores slowly let air escape.
 For this reason, carbon-latex bladders are used, in which the carbon powder helps to close many of the micro pores.  Compared to latex bladders, butyl bladders retain air for longer periods of time, hence providing an excellent combination of contact quality and air retention.

Stitching:  Professional and high-end balls are hand-sewn by expert craftsmen using 5-ply twisted polyester thread, while most mid-priced balls are machine-stitched.  Hand sewn balls have stronger and tighter seams.

All the factors mentioned above impact the quality and cost of a soccer ball.