>"Am I overlooking other cheap, outdoor-worthy (durable) fabrics that are more wind-resistant and lighter than polyester but with enhanced breathability?"
Momentum 90 at through hiker is light, reasonably durable, good initial dwr, but not cheap.
Strong, cheap = canvas (or cast iron), but heavy. Strong, expensive = spectra (titanium), but not cheap. Light, cheap = silk (balsa wood), but not durable.
Throw in cosmetic factors for materials (a nice hand, good drape, colors, texture, etc.) and your choices can get even trickier. Big gear companies usually opt for looks and durability that sells, and price and weight (and often functionality) takes a back seat.