You know the great thing about having $2 billion in cash? You can buy anything you want. Well, that's not totally true. You can't buy something that costs more than $2 billion, and if you're a company likeeBay (NASDAQ:EBAY), you'll need internal approval to spend, spend, spend.

What might be a good thing for eBay to buy? Well, if the company takes a look in its own backyard, it might find something -- and I don't mean the very same used toys, DVDs, and furniture most people have in their backyards. I'm talking about bricks-and-mortar auction houses. Two come to mind.

One is Greg Manning Auctions (NASDAQ:GMAI). We've seen twoarticles written about it recently here at the Fool, examining the complex arrangement Greg Manning has with Afinsa Bienes Tangibles, a collectibles company in Spain. Given the roller-coaster ride Greg Manning's stock has been on over the years, I got to wondering whether it might be an acquisition target of none other than eBay. Why not? What would be more juicy to Meg Whitman's behemoth than creating a monopoly in the auction world, assuming any acquisitions could meet regulatory approval?

Although Afinsa has bought up 72% of Greg Manning, that doesn't mean a bid (hostile or otherwise) couldn't be launched for the company. And given the questions that were raised by Afinsa's purchase, one has to wonder if eBay is sitting on the sidelines to see if Greg Manning Auctions hits another rough spot and the stock price plunges again. Right now, it's valued at $300 million, but there's always potential downside.

Add the venerable Sotheby's (NYSE:BID) to the list and things get even more interesting. The aging queen of the auction world is bigger than Manning: $1.1 billion in market cap and $217 million in debt. Still, the prospect is worth considering.

Investors should always be on the lookout for a company that does one simple thing really, really well. Because if it can buy up other similar companies doing really, really well, it just might make for a really, really great investment -- especially if it's creating a monopoly.

For related Fool coverage, see:

To talk with other investors about auction companies, go to the eBay, Greg Manning Auctions, and Sotheby's discussion boards. Only at

Fool contributor Lawrence Meyers owns no stocks mentioned in this article, which solely reflects his opinion and is not a recommendation to buy or sell any darn thing -- including your used toys.