Bank of America made headlines this week when it announced that it was offering free equity trades for customers who put $25,000 in deposit accounts.

Customers in the Northeast who put $25,000 in to such accounts get up to 30 free equity trades a month. The news sent shares of discount brokers E-Trade, Schwab and TD Ameritrade tumbling.

There’s got to be a catch, right? Of course there is. This is as close as the media got to uncovering it:

“Knowing there is no free lunch, consumers look carefully at the whole picture,” Charles Schwab told USA Today.

I found the catch in less than five minutes on the BofA Web site: the $25,000 doesn’t count toward your investment. At most brokerages, all of your stocks, bonds, mutual funds, savings count toward meeting discount thresholds. Under the BofA offer, you have to set aside $25k in BofA savings or checking accounts and then have additional money to actually use for the free trades.

When you look at the math, the free trades are about as free as the free World Series tickets you can get if you buy a pencil for $800.

In the New York market, BofA pays 2.25% on their money market account. Compare that with the widely advertised 5.00% that Citi pays on their e-Savings account. Over the course of a year, that’s a difference of $687.50 for those “free” trades. You pay that $687.50 whether you make a trade or not. You’d have to make 60-70 trades a year to come out ahead.

If you put your money in BofA checking accounts, you do much worse. Put it in BofA CDs and you do better. If you’re investing for the long term, you’d want to put that 25k in stock funds for an 8-10% yield, making the free trades a much bigger loser.

In a world where financial products are becoming increasingly complex, the media need to do a much better of dissecting these announcements instead of repackaging press releases.