I was once involved in a business enterprise with a man who wasn't a native speaker

I had talked to a child about buying some of our stuff, and he was psyched about it and went off to fetch a parent to complete the transaction

I was talking with my colleague about it in the interim, and said of the kid "he was sold" as a way of summarizing his receptiveness to my pitch about our products

My colleague became very alarmed. What do you mean, sold? Who bought him? What do you mean?

It took a while to explain.