your in Washington so thats good. You can buy a Glock 18 in the US and you can legally buy a registered machine gun. Just have to fill out the appropriate paperwork, have the local sherriff sign off on it and send it out to the ATF with $200 and then buy the gun. http://www.fullautos.com/ Fully auto guns are extremely expensive because a law was passed in '86 saying no more could be manufactured for civilian use so there is a limited number of fully auto guns out there. You can always try to get one illegally though.
In Virginia you can pretty much get anything you want legally if you have the money. My boy is about to get a Supressor/Silencer for his AR-15 right now. Let me know if you want to know anything else.
This is my AK only cost $300 out here but its only semi auto.