Apple (AAPL -0.65%) just made history: Prior to June 30, no stock had ever closed with a market cap of $3 trillion or higher. But the tech giant now finds itself the sole member of the club.

Arguably, no person on the planet benefits as much from Apple reaching this milestone as Warren Buffett. But what does Buffett think about Apple's $3 trillion market cap? Well, it's complicated.

A big stake and a big smile?

First, Buffett hasn't publicly commented on Apple achieving a market cap of $3 trillion. I would have been surprised if he had said anything. But we can probably get a sense of what he's thinking based on information that is publicly available.

Apple makes up nearly 47% of Berkshire Hathaway's (BRK.A 1.32%) (BRK.B 1.16%) total portfolio, making it by far Berkshire's largest holding. Buffett is Berkshire's biggest individual shareholder, with 15.6% ownership of the company. 

Buffett's net worth right now tops $114 billion. Apple represents nearly $27.5 billion, or roughly 24%, of that total. It stands to reason that Buffett would have a big smile on his face as a result of Apple's growing market cap. After all, the tech stock has added well over $8 billion to his net worth in just half a year.

I doubt that the legendary investor cares about the $3 trillion threshold. But he probably likes the positive impact that Apple has made so far this year on Berkshire's portfolio.

Buffett's different way of thinking

On the other hand, Buffett has a different way of thinking, meaning he could be less happy about Apple hitting the $3 trillion market cap than most investors would be.

Why in the world wouldn't Buffett be thrilled that Apple stock has skyrocketed nearly 50% year to date? Consider what he wrote in his 2011 letter to Berkshire Hathaway shareholders:

When Berkshire buys stock in a company that is repurchasing shares, we hope for two events: First, we have the normal hope that earnings of the business will increase at a good clip for a long time to come; and second, we also hope that the stock underperforms in the market for a long time as well.

He added:

The logic is simple: If you are going to be a net buyer of stocks in the future, either directly with your own money or indirectly (through your ownership of a company that is repurchasing shares), you are hurt when stocks rise. You benefit when stocks swoon.

Buffett told CNBC earlier this year that he "loves" when Apple buys back its shares because it increases Berkshire's ownership in the company. He stated, "We'll never own a business that makes so many people happier and useful for 'em." 

There's ample reason to believe that Buffett would like Berkshire to own more of Apple than it already does. But he isn't going to buy additional shares unless the price is right. The reality is that Apple's massive market cap could get in the way of Buffett buying more of the stock.

More mixed emotions

I suspect that Apple could stir more mixed emotions for Buffett over the next few years. Roughly one-fourth of the company's customers haven't upgraded their iPhones in over four years, according to Wedbush Securities' Dan Ives. That could set the stage for a big boost from upgrades in the not-too-distant future.

Apple's services business could be its biggest growth driver, though. And don't forget about the company's Vision Pro mixed-reality headset. Sure, the high price tag of the new product could limit initial commercial adoption. However, subsequent lower-cost versions, combined with creative financing plans, could change the dynamics.

A $4 trillion market cap for Apple within the next few years isn't unrealistic in my view. The stock will likely make Buffett much richer -- even if it doesn't make him happier.