Opportunity Cost of Science

It is extremely difficult if you've got wads of cash to decide who you should give it to. Economists have concepts like 'opportunity costs' to try and estimate how much doing something will cost you or converesly what not doing might cost you. I think its easier to just think about it in terms of a bet/insurance policy. What are my odds of payback? Does the payback justify the cost of the bet? Is this the best thing i should be spending my money on?
Science funding is particularly tricky because most of the time the big breakthroughs come from the places you least expect - this is often used by mediocre researchers to justify their research i.e. "nobody thought messing around with soot would lead to buckyballs, hence you should give me a million dollars to build my perambulator 3000".
Into this cesspool of biased opinion and vested interest i am going to throw 'manned space research'. Note the use of the first word: i think building robots that land on mars and outperform their life expectancy by 3-5 times is exciting and worthy of the deepest kudos, peering into the furtherest expanses of space hunting for clues on the origins of the universe is a defining pinacle of humankind but lobbing a couple of glorified chimps a half-dozen miles off the surface of the earth so that we can then read media reports of their lunch and observe the effects of microgravity on crystals/ants/seeds (hint: sweet FA) is cheap theatrics at best, a marketing exercise designed to bleed more money from the gummint at its worst. Why oh why is China following in the footsteps of the whitest of white elephant projects even NASA can't jettison?? Is this a global pissing contest? I mean let's get serious people, China is growing at a fantastic rate and it is highly likely that a lot of the best research this century is going to come from China/India, why is China wasting its precious research funding on manned space flight? Surely they have mouths to feed, environments to care for, diseases to cure and energy to provide???
Every billion you spend in one place is a billion less somewhere else...
For some truely awe inspiring reporting check out New Scientist where you can learn such fascinating trivia as:

In the Shenzhou VI mission, the two crew members can shed their bulky space suits in the orbital module, take turns resting in sleeping bags, and have use of a toilet.

They can also warm their meals, which include 50 menu items including beef with orange peel, rice and strawberries. But the reduced gravity means they will have to forego the use of chopsticks in favour of forks and spoons.

I mean good grief, the only thing left is a survivor/big brother website where we get to vote one of the taikonauts into an airlock. Marketing hype 1, real science 0