@evildictaitor: So, let's say I've come up with an idea, I go to the patent office and have it patented.
What value have I added to society that I should get paid for?
None. That's why you don't get any money for filing a patent. In fact, it actually costs money to file a patent, so if you patented a "beard-extensions - like hair extensions for your beard!" or a "cheese-powered lamp", you're probably going to be poorer for patenting it. And since patents expire, you can make yourself very poor by patenting stupid inventions and sitting on them.
Patents are not a magical money machine. They have no value unless they have patented an idea that someone wants to build and expects to sell for profit. And the government does not "assign" them a value.
Your patent only has value if someone else wants to buy it off you in order to make the invention (or in order to sell it on further). And the specific value? Whatever the buyer and seller agree is the price.