You're basically using capitalistic model to better rate the "value" of a news item--hence an economy/market based on trading(buying/selling) news, instead of using a basic democratic process modeled after political organizations (which is what digg/reddit/yc is modeled after).
I think it makes sense for those that understand basic supply/demand and capitalism ideas, such as "decentralized market determines price", "invisible hand", etc. But for those that don't, they'll have a hard time with understanding why they're buying web links with no inherent value with virtual 'dollars'
I assume lambdas are unit of exchange--price. You might want to call it something that people can infer are money...like "rupies", "newsdollar", etc.