I recently changed one of the tires of my old car for only $45, I was told it was a "second hand" tire, but it looked pretty new to me. I used to change tire at

I recently changed one of the tires of my old car for only $45, I was told it was a "second hand" tire, but it looked pretty new to me. I used to change tire at the Costco tire center, where I though I got deals. They usually suggest changing at least 2 tires each time and asks for at least $250 after some member discounts. I also recently purchased an Audi and was told that each tire of an Audi will cause $400. I wonder why it is so expensive and if I could still go to the store and purchase a second hand tire for the Audi. I don't know what it means for "second hand" tire. I remember this youtube video about recycling tires https://www.youtube.com/watch?v=ERDIsONgSCQ https://www.youtube.com/watch?v=ERDIsONgSCQ I guess tires can be renewed? I also know they can be used to make shoes.