Yes it's a good lesson learned but there is another lesson here as well. Don't buy or sell to this dealer again. He took advantage of a person new to the hobby and he'll do it again.
But here's the thing, this dealer talked a good game. My son, while not totally innocent, I'm sure he ended up trusting the guy more than he should have. But what my son felt was the dealer was friendly, and that disarmed him. I'll talk to him about that.
I'm referring to the dealers character. He did it once. He wouldn't hesitate to do it again. Be it you, your son or another individual. I'm simply saying, avoid this dealer. There are plenty of others to do business with.