Price and sometimes weight varies by Location, availability, and kind of weed.

actually only the dime and nickel should vary in weight, as they are called dimes and nickels because of price, not weight

a straight (not bullshit) eighth is 3.5 grams... a quarter is 7... and so on

Schwag (normal, crappy, just above ditchweed pot)
nickel = $5 = 1-2 gram
Dime = $10 = 2-3 grams
Eighth = $10-$20 = 3-5 grams (depending on dealer... 3.5 is straight)
Quarter = $15-$40 = 6-10 grams (depending on dealer... 7 is straight)
Half = $30-$60 = 12-18 grams (depending on dealer... 14 is straight)
OZ = $50-$120 = 24-34 grams (depending on dealer... 28 is straight)

Pretendakines (midgrade)
Nickel = $5 = .5-1 gram approx (fair sized bowl, maybe 2)
Dime = $10 = 1-1.5 gram
Eighth = $30-$50 = 3.5-5 grams (if your getting charged 50, ur gettin screwed)
quarter = $60-$100 = 7-9 grams (again on the price, just cuz its good dont mean its kine)
half = i think you understand basic mathematics

Kine bud (High grade)
Nickel = you arent gonna find a nice enuf dealer
Dime = $10 = approx .5 grams (usually a small bowl, eyed not weighed)
Eighth = $50-$70 = 3.5-5 grams (if its less than 3.5, tell the guy to fuck off)
Quarter = $100-$140 = 7 -9 (if less then 7, again, he can go to hell)
Half, OZ, Qp... again... you know math, right?