All my stoners wya

So I clearly don’t smoke and my boyfriend just casually asked me to get an eighth (just a guy who sells not a dispensary). No biggie I’ve just never done this before bc I’m a 21 year old amateur lmao. I don’t even know how big an eighth is.

Anyway so my question is how much does it usually cost? Bc I don’t want to be ripped off bc it’s very obvious I’m oblivious to this sorta thing

Help pls