Jiejie is correct, you will have to pay for a rip off tour. North Korea is not a country you can just visit, especially if you are a US citizen. Since you are a US citizen, I would not try to get in via the back door as it will surely get you arrested or worse.

Having said that, some of my non-US citizen friends have visited and I hear Pyongyang is quite an unique destination. But please consider that you will be essentially enabling a despotic regime by giving the bankrupt (both morally and financially) government valuable hard currency. I do not want that on my conscience, but of course you are free to do as you wish.