I've been there a couple of times and always pay about $10/gram for decent shit. Some really nice strains can even pull $20/gram. Every shop sells by the gram and you're allowed 5 grams a day.
Now, there is a whole illegal marijuana system as well. So, if you want more than the 5 gram legal limit or want better prices for bulk, you can find dealers in the red light district downtown. Personally, I wouldn't fuck with these people - they're dangerous. We got chased (and almost robbed) by a 300lb man from Bulgaria while there and I'll never go back to that area of Amsterdam again. I stay in the legal shops, buy my 5 grams per day (which costs around $80 buying nicer strains) and compile that shit up. If I smoke only 3 grams per day, I can get 10 grams to take with me after 5 days.
Now, weed is cheap in Amsterdam, but everything else is expensive as fuck - especially hotels and hostels. Expect to pay out the ass for food and lodging. You will spend up to $100 day on bud, but upwards of $200-$300 dollars a day on lodging and food. Seriously, it's expensive. They're also shutting down a lot of the coffee and sex shops, so even weed is becoming more expensive. However, it all depends on how you buy it. You can pay $5 a gram for shit or $20 a gram for some fire!
Hope that helps - if you have more questions, ask and I will answer. An ounce might be difficult to bring back, but if you're savvy and have good people skills, you might be able to pull it off...
