Double RL is Ralph Lauren's heritage workwear label, positioned above the main Polo lines and sold through a small number of dedicated stores and stockists rather than through department stores. Its design language borrows from early twentieth-century American workwear and military clothing: denim, chore coats, flannel shirting, field jackets.
Production volume is a fraction of Polo's. That single fact explains most of what follows, at retail and afterwards.
Two things drive the retail gap. Double RL has long sourced denim from Japanese mills weaving on shuttle looms, which produce a narrow, self-finished width at much lower output than the projectile looms used for volume denim; the fabric costs more per yard mainly because of throughput, not because the yarn is inherently superior.
The rest is finishing and labour. Heritage-style washes, distressing and hardware take more hands-on work than the equivalent Polo garment, and short runs spread development and setup costs across fewer units.
Secondhand is where the gap widens rather than closes. Polo produces at a scale that keeps the used supply of almost any given piece deep, so asking prices settle toward a floor set by abundance.
Double RL pieces surface in ones and twos, and the people looking for them usually know the specific model they want. That is why a worn Double RL jacket can ask more than a new Polo one. The scale difference is visible on the Polo Ralph Lauren page: the volume itself is doing the pricing.
Selvedge is something you check rather than something a listing tells you. Turn the leg inside out and look at the outseam for a clean, self-finished edge, often with a coloured line running through it. Labels vary by era and are the weakest thing to judge from, so read the whole make instead.
On condition, surface fading and whiskering are cosmetic and frequently desirable. Thinning at the crotch and seat, blown belt loops and replaced hardware are what actually cost you when you resell. If the asking price lands near new Polo money, decide whether you want the fabric and the cut or only the look.