New parts are a dog eat dog race to the bottom on margins with more choice than ever, markets for used parts are more liquid than ever and there’s a guide for everything.
I can google some vague OBD code (yes, the car will tell you what’s kinda going on!) with my year/model and someone will have a step-by-step guide on “oh, it’s 99% this $11 part, if not, check that”.
My own experience with an insurance claim after getting rear ended was this: take it to their preferred shop, or we could choose a licensed autobody shop (they would pay $2800), or cut us a cheque for $1900. We took the cheque and our mechanic fixed it for $950.