The cost depends on the difficulty of the subject and how soon the paper is needed.

VOA: special.2009.04.23

And now Steve Byers has got the difficulty of how making the changes for implementing basically a better railway system.

BBC: News | BREAKFAST WITH FROST | Deputy Prime Minister John Prescott

Because of the difficulty of estimating how many doses were sold, returned, or discounted, MedImmune couldn't book sales.

FORBES: Is There Hidden Value In MedImmune?

But he notes that competitions have drawbacks too, such as the difficulty of determining how much an innovation is worth in prize money before it is used.

WSJ: Prizes Abound but Unclear if They Are Best Way to Get Innovation