A desk fan, because it's hot.
Most items on Amazon just aren't worth it anymore. The cut Amazon takes goes too far into margins that only the products with the highest margins (lowest production costs) remain on the platform. I assume the desk fan I'm getting is going to be cheaply built, but I don't need it to be amazing for a simple job.
Some big brands are worth buying from on there, but they must either have a deal with Amazon or only discount a small amount. And then typically the discount they do give will be echoed elsewhere at some point.
Prime Day is not a good time for a bargain. Black Friday is still okay, but again only really for big brands.