For a lot of the cheap stuff on Amazon, the price is literally double at a local brick and mortar retailer. Phone chargers, kitchen utensils, towels, cleaning products are high-margin examples that come to mind. Plus, of course, your time and gas money to grab it. Some people also struggle with impulse purchases they may grab while shopping in store. Its easy to see why people continue to throw money at creepy Bezos and just wait for shit to appear on their porch.

The ads can be variable length and tailored to whoever is downloading the podcast. SponsorBlock for podcasts does indeed need to be a thing (but it may be tricky to implement and easily subverted).

The ads are put in by whoever makes the podcast.