I dont think you can price data like you price, say, a tractor attachment. Data is more like pricing a valuable antique because the value changes as the data is, or is not pertinent, young, old, etc.
For example, I know people who swear by their PDA's and I often ask "How often do you back it up?" - the answer is inevitably "Never". So that data obviously is not worth much to them - until they drop their PDA which gets run over by a passing street cleaner and then suddenly, that data is "priceless".
Or how about the really slick criminals who hacked into a system and stole a vast list of credit card numbers... and it turned out that the list contained only cancelled credit cards.
And therein lies the problem. You cannot put a price on data because its largely subjective and time-bound. What you call "valuable data" is, to someone else, junk.
As well, consider ALL the data that gets thrown up on the web - not just business data! Here on the east coast we have been in the middle of this recent flap over Professor Gates and Sgt. Crowley of the Cambridge Police. But then a Boston police officer named Justin Barrett posted one of the most hateful and ignorant messages, full of racial epithets, on the web!
Now is THAT "valuable data"? Think about that - what if you were going to hire this guy (or one like him) and someone else came along and showed you a copy of his hate-laden posting? Would you call that "valuable data"? It is data - and to someone not interested in hiring racists, it would be valuable - but to Justin Barrett himself - is that valuable?
People need to think outside the box a little. We always seem to think valuable data is only business data - its not. Especially in this day and age of people throwing things up on the web that they cannot take back.
There's no such thing as dumb questions, only poorly thought-out answers...