The video starts with a narrator saying that he will be talking about how to get cheap aftermarket auto parts for your car.
EBay is a great platform for getting cheap aftermarket parts. You can find slightly used parts for a really fair price, just make sure the seller is legit.

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Craigslist is also a great network for getting aftermarket car parts. You can get sellers from near your area. Make sure you meet during the day and in a public area for your safety.
Buy aftermarket car parts during the holidays. Most sites offer significant discounts for the inventory they have on hand. Black Friday is a great example of a holiday that is filled with discounts. You can also visit your local metal fabricator. They offer competitive pricing for their in house parts and may sometimes install the parts free after purchase.
Regardless of the type of aftermarket car part you are looking for, you are guaranteed a discount. You can also go to your nearest junkyard to salvage parts.