How to Ruin Your Car Stereo While Saving Money at the Same Time

Graham has been a saver since day one. Before he was even born, he had a savings account at the bank, and we've been trying to teach him habits of frugality ever since. But today I found out that not all saving is good saving. Sometimes it can even cost you money.
For the last couple weeks the cassette player in my car has not been working. What's the big deal? you ask. Cassettes are so 80's. Who uses them anymore? The iPod, that's who. AM/FM modulators do not deliver good sound, and there's too much interference for consistency. I prefer the cassette adapter. I have about 20,000 songs on my iPod, as well as scores of podcasts, radio broadcasts, and books on tape. I am a full-bore iPod addict. Which brings me back to the point of this story: without the cassette player on my car, I've been stuck listening to the NPR pledge drive over the past two weeks.
So I got on eBay and ordered a new one. Well, not a new one, exactly. A refurbished model of the exact same stereo I currently had. $80, with shipping. Far better than the $150-200 for a quality aftermarket model, to say nothing of the $400 for a new GM system. It came today, and I installed it tonight after dinner, a five minute job. And what should I hear as I pulled the old stereo out of the bay? Jingle.
Jingle? you say? Yes, jingle. As in coin. Lots of coin. Lenient father that I am, I've been letting Graham sit in the front seat of my car when I'm trying to get work done around the ranch--like split wood, rake leaves, etc. He is content to sit there for hours, "dwiving daddy cah." But apparently he's also been on an aggressive savings program. By the heft of the old stereo and the sound of the coin, I'd say he's probably got most of the books for his first semester in college covered. Of course, the $80 I had to pay for a new stereo will take a bite off of his profit margin. Anyone interested in a GM stereo with AM/FM, CD player, and NO CASSETTE?