I do beleive that this letter was worth the price it sold at. People like to collect things, and many of them like to collect old things. I think that this love letter is a piece of history. I also think this sold for so much because of how popular the 2 celebrities were.
Any time there is a high-dollar sale of a notable item or collectible, many people like to come out and question whether it was really worth that much money. For us average Joe's working middle class jobs, that figure is more than most people's average salary, and so it seems like an absurd price. But for the very rich with tons of disposable income, why not pay that much for this item? After all, it's a great collectible from the annals of American history.
When Dimaggio's love letter to Marilyn Monroe sold for $78,000, I was livid. While Dimaggio was certainly a talented athlete and Marilyn was certainly the beauty that is remembered, America's fascination with the private lives of celebrities is out-of-hand. With every other popular show an inside look at some stars' private lives, it's more appropriate now to get in touch with things that really matter, like our own families or communities. $78,000 is more money than a lot of Americans make in a year! Yuck.
The letter is priceless and should have been kept private within the family. I'm sure he would be horrified to find out anyone else was reading his private thoughts to his wife that were difficult to articulate. It's like an invasion of privacy unless he had allowed the letters to be seen publicly, but given the content, I doubt it.