This was more than just Buffet's good timing in making an investment. He was also renting out his reputation. Goldman Sachs's future was in question, so the vote of confidence from Warren Buffett, the so-called Oracle of Omaha, was very valuable for them. Thus, the deal was structured to be very lucrative for Buffett. No comparable investment opportunity was available to the public at the time.
Warren Buffett is very good at what he does, but he also has opportunities which just aren't available to the general public.
He has also long argued that investors with much money have far more attractive investing opportunities. If you're controlling tens or hundreds of billions, small caps don't even move the needle on your portfolio if you buy the whole company! At Berkshire's size high growth investments are very hard to come by. The almost have to be something exceptional like this.
Well, you can invest in Berkshire Hathaway stock and be sure that, unlike the evil idiots at Goldman Sacks, Buffet will be managing your money in your long term benefit, and putting it in those far more attractive investing opportunities in your behalf.
Last I heard, BRK.A trades at a pretty hefty premium above the market value of its assets (not something you normally want to see in a holding company), and nobody knows whether a protégé of Buffet will be able to come anywhere near his celebrated performance.
Buffet himself does not believe that will happen. If you read the 2010 letter to shareholders, he states that going forward he does not expect growth in the order they have in the past.
That he and Charlies biggest challenge is to maintain a solid baseline of market matching, and occasionally beating, performance. They can't really go for the big wins any more - due to their market cap, a big win would have to be astronomical to give them growth like they had in the 80s.
Warren Buffett is very good at what he does, but he also has opportunities which just aren't available to the general public.