The Netherlands
There are standardized prices (every coffeeshop has their own, but this usually makes no real difference. It varies a couple of euro's here and there, so 5 euro's = sometimes 6 or 7 and ofcourse the amount of weed goes up and down too), the coffeeshops usually sell baggies for 5, 10, 15 and sometimes 20+ euro's that are listed on the pricelist and often already are pre-packed.
You
can ask for a certain amount and pay a certain price, but there are so many different sorts of weed and coffeeshops that it seems impossible to list every single gram and the price that goes with it, I'll just list the rough standards.
5 euro's - from A1 (~0.5 gr) to C1 (~2.5 gr)
10 euro's - from A1 (~1.6 gr) to C1 (~5.2 gr)
15 euro's - from A1 (~3.5 gr) to C1 (~7.5 gr)
20+ euro's - unlikely, but expect a large amount.
Pre-rolled joints are usually ~2.50. You can get pre-rolled hash joints, weed only and joints mixed with tobacco. Weed only and hash joints will cost a bit more (like 0.5 euro's more or something

).
If you think I've made a huge mistake and/or think you can add something to this post, I'm more than happy to receive your PM and make some changes.
I'll shall go ahead and also name some of the prices my local dealer gives me..
5 euro's - A2 (1.1 gr) to A4 (1.6 gr)
10 euro's - A2 (2.4 gr) to A4 (3.2 gr)
15 euro's - A2 (3.8 gr) to A4 (5.2 gr)
I don't know how much he gives me above 20, he goes as high as 30 per bag and that's enough to last a good while. He's awesome cause of the good prices, but still hasn't got the greatest weed out there.