In this day and age, I would never carry something for someone this way. It's such a bad idea. You could land in prison. Even if you're taking books, the spines might contain fentanyl. And I have no idea how you get past that.

That being said, there is a long-established business for this kind of thing for companies, not individuals, that goes back decades. Here are two examples:

1. 30+ years ago companies would give discounted tickets to people with the condition that they couldn't take any luggage. Why? Because the company would use their luggage allowance to send stuff. I believe it was mostly documents. Discounting an airfare by $500-1000 to send 50-80lb of documents was actually a good deal. I don't know how the logistics worked of baggage drop off and pick up but I believe it was relatively understood that the passenger wasn't responsible for the luggage. I assume the shippers had some kind of commercial relationship with the airline and handled all the customs declarations, import duties, etc;

2. There are times when businesses need to get certain parts or materials in a very time-sensitive manner. For example, I knew someone who worked in oil and gas. An oil platform had shut down production and needed a replacement drill part or something, I forget, and it was over Christmas. They could've ordered it. It would get sent and then sit in a customs warehouse until it gets cleared. That could take days or even a week or more. Not having it was costing half a million dollars a day. So what did they do? They flew someone across the Atlantic to the US to get the parts, pay exorbitant extra baggage fees (it was large) and come back with it. Why? Because passenger baggage would immediately pass through customs at the airport. This would likely save 5-10 days.

So there are some obvious questions to be asked here like:

- How do you make this safe and legal?

- Why isn't this just being Fedexed? Fedex is your cap on fees too;

- How does someone pick this up and drop it off?

- What if they get charged customs fees? How is that recouped?

- Who fills out customs forms?

- What about transiting countries? You may run into issues where something is legal in the source and destination countries but you transit somewhere where it isn't.

I don't know how you bootstrap this because you're going to be dealing with people who have way more experience than you at shiping thing sinternationally. More importantly, they'll have much more volume. That means they can send things via courier at rates you can't dream of getting. So how do you compete with that?

Even in the example mentioned above, the company used an employee to go pick it up. It was an expensive part so an employee could be trusted more than some random could.