depends if you want crap weed, or weed that's been grown and treated properly budolskie. you'll be sure to get some nice weed at the "Grey Area", but it isn't cheap (15 euro for a nice kush - og, or candy kush or something, but then no where in Amsterdam is cheap anymore). The larger shops charge anything up to 18 euro, I think the Bushdoctor are selling BHO wax (which is illegal to sell) for 95 euro a gram
There are good places, you just need to hunt around. Always ask to see the weed (they don't like you picking it up though) and don't feel uncomfortable saying, No thanks! The thing is, it can be a lucky draw, some plaes will just have a good batch of something in, the quality is not always 100% consistent throughout all places.
If you get on a 17 tram and get off a Bilderdijkstraat there is a coffeeshop called Cheech and Chongs, they only sell a couple of types of weed, but it's always decent and well priced. And they sell the best moroccan hash in amsterdam (imo) It's called Tbisla...pronounced Tuh-bee-sla....it's worthwhile going just for that. IF you don't want to get a tram you can walk it, but it's about 2km (but on a straight road straight from behind Dam square - Raadhuisstraat, goes into Rozengracht, which eventually turns into De Clerq straat, and thats where the shop is.