The other morning, my six-year-old son wanted to take to school his collection of roughly 100 Yu-Gi-Oh cards. For those unfamiliar with this impossible-to-understand, Japanese-inspired game played with collectible trading cards, I'm afraid I can't be a lot of help. But think of the card games bridge and battle jumbled together with cryptic rules, then throw in an army of mythical monsters, magicians, dragons, magic spells and a bubonic rodent.

The thing about these cards is that just as with the mindless euphoria that swept the Beanie Babies market a few years ago, Yu-Gi-Oh card collecting is hot. A box of 50 cards costs about $13, but some of the individual cards fetch $80 a pop. A particular set of the five most powerful cards sells for $250 or more. I know; I searched eBay for an unopened box of hard-to-find Yu-Gi-Ohs that my son talks about frequently and that Amy and I gave him for Christmas.

Given these prices, I told my son he couldn't take his collection to school. The cards might get crinkled and then be worth nothing.

He looked at me in disbelief. Who cares what they're worth, he cried, calling me a "stupid dummy." But I stood my ground. "One day you'll thank me for being a stupid dummy," I told him, "when your Blue Eyes White Dragon is worth a lot of money."

But on the train into work later that morning, I started thinking about the baseball cards I collected as a kid. I remembered my friend Jim and I desperately trying to convince his baby sister, Michelle, to give us her 1974 San Diego Padres team-photo card because she was the only kid in the neighborhood who had it -- and she didn't even care about baseball!

And then it hit me.

We parents have been so warped by the whole collectibles phenomenon that we can't see what we're doing to our kids. We hear that a mint condition 30-year-old Barbie or G.I. Joe still in the box is worth a gazillion dollars today, so we lament ever having ripped into the cardboard. We see a Ty Cobb baseball card sell at auction for more money than we'll know in a lifetime, and we cringe thinking about that Willie Mays rookie card we stuck in our bike spokes.

My son was right: I am a stupid dummy.

* * *

Despite what we have been brainwashed into thinking, collecting cards or coins or camel figurines isn't about the money they might one day be worth. It's about being a kid. And being a kid is nothing if it's not playing with your toys.

Think back on your own childhood. If your dad told you Christmas morning that the Rock'em Sock'em Robots that you just opened would be worth hundreds of dollars years later, would you a) gingerly place the box on your top shelf and never touch it, awaiting the day you could sell it for oodles of cash, or b) look at your dad like he was a stupid dummy and rip apart the cardboard and start rockin' and sockin'?

I ripped into mine, too.

And I don't regret it. That now-collectible toy isn't just a semivaluable piece of kitsch from the '70s; it's part of the memories of my childhood I hope I never forget.

I mentioned the Yu-Gi-Oh cards episode to a friend at work, and he told me of his own baseball-card collection built in the early 1960s, and the collection his son built 30 years later. My friend played with his cards like all of us did before sports cards became currency. He still has his cards; none are in mint condition. When he realized how valuable they might otherwise be, he says, "I momentarily regretted spending years flipping them. But that's silly. They were so much fun to flip."

His son, meanwhile, kept his cards unspoiled, placing them in archival-quality plastic sheets. He says his son's only interaction with the cards was "getting caught up in what they were worth. He never looked at them or played with them. He only looked at the price guide. It sucked all the fun out of the cards." Now, his son doesn't have the same attachment to the cards that my friend has to his.

* * *

If a kid wants to keep a collection of cards or dolls or Hot Wheels in pristine condition, that should be encouraged. But it should come from a child's own desire and initiative, not from a parent's misguided notion that Stripes the Beanie Baby tiger will be worth some nonsensical sum if only its tag is left unmolested.

A woman I work with says one of her young nieces has collected Barbie dolls for years, and now has a large assembly displayed in her room. All still in original packaging. All unopened. "And it was all her own idea," my friend says.

Though the family encouraged her to play with them if she wanted, they also supported her desire to preserve the dolls in mint condition. "Part of me wishes she had played with them," my friend says. "But at the same time, I see that it took control and commitment to build up a collection she's proud of and that's worth quite a bit. She has a great sense of accomplishment."

* * *

I still have my baseball cards -- thousands of them stashed in plastic crates. I was rummaging through them recently, thrilled to feel the rough edges of flimsy cardboard before sports cards went up-market glossy. There they were, the stars of my youth -- a young Nolan Ryan, Carlton Fisk, Reggie Jackson. Cal Ripken Jr. in his rookie year. I felt like a kid again.

And I realized the value of my card collection isn't the money it can fetch now (perhaps quite a bit, since many are in mint condition), but rather the memory of coaxing my grandmother to drive me and Jim across Baton Rouge to the Walgreens on the farthest side of town to buy a box of cards because we thought a different store would have different cards. It's laughing at Gates Brown, Detroit Tigers, circa 1974, because he had a funny name and we seemed to get his card in every pack.

That's the value of collectibles I want to share with my son. Who cares if one day his Blue Eyes White Dragon is worth 10 cents or $10,000; the memory I hope he recalls is the joy I saw on his face that day in the car when we opened the pack and found Blue Eyes -- a card he'd talked about for days -- sitting on top.

He can lose it, trade it, sell it, save it. I no longer care.

They are his to play with.

Jeff D. Opdyke is a staff reporter of The Wall Street Journal.  To contact Jeff, send an email to  lovemoney@wsj.com.