They do exactly that, but sometimes, it goes wrong. It happened to me in October 2019 and I'm still trying to get out of this nightmare.
I bought a high-end desktop for $2700 from amazon, it was shipped with a GTX 660 instead of a RTX 2080Ti! The graphic card had been swapped by the previous person and Amazon blames it on me.
- They say they checked the item before sending it, they obviously didn't
- There was no indication when buying that this item had been previously returned
- They say I did this scam several times before but I order a couple of times a year and for low value. I never returned anything
- They refuse to listen to me and consider they made a mistake. The India-based chat support is entirely useless, they keep telling me "there is nothing I can do", "so sorry", etc. I sent an email to jeff@amazon.com and they tell me "we'll not be able to offer any additional insight or action on these matters, and any further inquiries on this matter won't receive a response."