I think it is plausible that if you lived in the U.S. for a year or more and came back across the border with a trailer full of furniture, including a pinball machine, you could be successful with the " I was at school in the States and now I'm moving back home" routine. If they pulled you over, went through your stuff and asked about the machine, you just give them straight-forward answers. Living in the U.S. for a while gives the scenario a new 'twist' and might just get you through without penalty.
Just have the invoice ready in case and don't play word games or mind games. Most of the agents have a sense of humour, but THEY like to dictate the tempo of the interview. They often misinterpret jokes, smiles, etc, as attempts at evasion.
The circumstances under which I have brought pins back have differed greatly. Almost every time I have gone over, picked up a pin and headed back just a few hours later, I have had to pay the 13%. However, once I spend a night or two in the U.S., I end up paying the taxes about 50% of the time. Mind you, I am talking about machines worth between $500 and $1500. Staying over a night or two would probably mean nothing if you were dragging back a Cactus Canyon.
A few times, I have stayed about a week. I paid about 33% of the time when I did that.
And once, I stayed about 3 weeks. Brought a Playboy pin back from San Diego. ( No, I didn't drive down there just to get a Playboy ). That was wave through city even though it was a little more than my personal exemption it was a no-brainer for the agent, especially with 3 of us in the car.
Long story short ( too late ), each border crossing is like a box of chocolates. However, there has been a movement in the last couple of years to tighten things up and the likelihood that you will pay something at the border in increasing.
