Composite Materials
There are several different types of composite materials used today, and each of these need different types of processes and the appropriate skills to understand and work them. They all have different performances and associated cost.
Glass
Carbon
Kevlar woven fabrics
Polyester, vynalester, epoxy resins
And pre impregnated systems
Glass and polyester being the cheapest, for low performance things like spats, to pre-preg carbon, the most expensive for high end performance like a full fuselage