I think an easy way to think about this is to invert the problem. Before venturing into any side hustle, it's useful to ask what value proposition you're offering. Take dropshipping, for example.

The opportunity to pay $15 for a lousy cotton t-shirt and then having to wait 29 days for the privilege of having it shipped to me from some random warehouse in China is not what I would call a "great deal."

But come up with an ethically-sourced superfine cotton t-shirt made by workers paid a fair wage, throw in 3-day guaranteed delivery, and a one-year no-questions-asked returns policy, and you might persuade me to part with $50 for a t-shirt. Figure out how to do this repeatedly and at scale, and you have yourself a lucrative side hustle.