As an actual Washington state resident, I'd have to say, join a Co-operative. If you are in Western Washington, your options are virtually endless.
www.thcwa.org <--I am a patient at this cooperative. Membership is free, but they require you have all of your documentation. Once you show them your documentation - ounces for $240, choices of around 6-10 strains, depending on when you catch him, and he delivers to YOU within 1 hour if you are on the north end. No delivery charge if you're in range. As far as "on the street", I don't support buying illegal, because I feel the state has come so far in helping us operate within the law. That being said, the prices should be comparable to most delivery services. If they are charging you more than $250, per zip, in Western Washington, YOU ARE GETTING JIPPED.
It's also worth mentioning there isn't more than a $10-$20 difference, per OUNCE. Most weed around here is considered "top shelf" to other states (excluding some of the other green states). So don't let a dealer tell you "oh its top grade, so im selling it for blah blah more than this guy". He's ripping you off.