The fast-fashion-versus-investment-piece decision isn't really about morality or trend-chasing - it comes down to cost-per-wear, and that calculation looks different for every category of clothing.
An item worn weekly for years easily justifies a higher upfront cost if it lasts, since the effective cost per wear drops steadily over time - this favors investment pieces for wardrobe staples worn constantly.
An item tied to a specific trend that will look dated within a season rarely justifies investment pricing, regardless of quality - the item's useful lifespan is limited by the trend itself, not the garment's durability.
Some higher-priced pieces are priced for brand rather than construction quality, while some affordable pieces are genuinely well made. Checking material and stitching quality directly, rather than assuming price reflects it, avoids both overpaying and under-investing.