So, I havent been since '06 so with inflation the dollar has become much weaker. As we speak a US Dollar is worth 0.710429099 Euro cents. So, when you are spending 20 Euros you are actually spending 28.15200 dollars. For the sake of clarity (cuz weed prices there can get pretty precise) I will use a personal experience. When I was there you could go to Bluebird (im pretty sure) and get 5 grams of Blueberry for 20 Euros. Smoking 3 grams a day you would need to re-up 4 times coming in at $120.
I dont suggest you do that though. I suggest you be extravagant and buy what ever you want. For example: We rolled in to town and passed places by until we found the one that just seemed right and then went in that one. They had only 5 selections I think and we chose 'AppleJack'. It was like 7.25 Euros for .7 grams and damn was it worth it. We had not smoked in about a week because of our travelling situation and it was such a nice fit.
We were so taken back by the experience of walking into a store, ordering some weed at the counter and then sitting down to smoke it that we had to get up and leave.
Back to the point. .7 grams at 7.25 euros comes to $10.2051 If you were smoking 2 of those bags a day for 7 days it would be $142.8714.
The stuff is definitely plenty cheap for you to go overboard. Look for the original SpaceCakes. Ask around and you will find them. Seriously though, dont go overboard with them. They might take a minute to kick in, but if you have never seen anyone OD on marijuana wait for Amsterdam. People go there, eat the space cakes and an hour later it still hasnt kicked in so they eat another one and maybe even another one. So many tourists get to experience the 'dam hospitals because of this.
Oh yeah, of major importance is the etiquette. It is not considered impolite for you to go in to a coffeeshop and just buy weed then leave. People dont even mind it when you come in to their place and dont buy weed; so long as you buy SOMETHING. A whole bunch of the coffeeshops sell fresh baked goods and I suggest you try things like that, if not you should get a drink. You will probably notice though that a lot of the coffeeshops are PACKED. Obviously I would just leave, but it is very amusing for people watching. Very amusing. I noticed a lot of smokers bravado though too. Guys will come in and burn 2 bongloads to their head and then smoke a blunt to themselves. I really did get the feeling that Americans were trying to show off for other Americans in the shop.
You can forget everything I said above if you want but, one thing you must remember and trust me on is Dont ever buy anything from anyone on the street. Likely it is schwag or evan a lot of times the same 'legal weed' you can buy in the states.
I was in Amsterdam for like 15 days and we consistently ran in to this same guy on the streets (4 times). " My friend, My friend, If you smoke the finest Marijua...", "no man, no man, we're good". Every time, the same line. The best part was that he would beat out any of those people they got playing Bin Laden in those communiques in a look a like contest any day. He had the accent and everything. I was also lucky enough to stay with locals that warned me of this ahead of time.
Ok, away from the weed.
Dont make any arrangements ahead of time with any boat deal or anything. wait until you get there. While the canals are beautiful in the aspect of how they are architectually integrated with the city but it is personally not as appealing as I would find a night on a boat in a beach front area, however the lights could be fun. The canals are very dirty and littered. If you do enough walking, which I suggest, you will see half sunken boats, mopeds, bikes and even cars. Just imagine all of the things that are fully sunken, preventing the half sunken things from going any further....But it is all part of the experience....
Honestly, I advise anyone that is passionate about smoking to save up your money and go. You can see beautiful scenery anywhere. Amsterdam offers you a taste of a culture that can not be matched.