weed sells in japan by the gram, not by 20's. therefor, a gram is anywhere from 4,000yen (about $35) to 8,000yen (about $70). there is really good fire in japan if you ever make any friends who sell. then you usually never have to pay the $80 prices.
I get the bomb all day long for $40! sounds expensive, but thats good prices in japan. its not bad in the long run, just dont smoke 5 blunts a day and ur coo!