20 can be bad/a rip-off, but it can be legit as long as it's dank. I payed $20 for some dank that smelled like a skunk a couple weeks ago. Depends how bad you want it.
i remeber the first time i smoked alone i bought a bubbler off mf my friend and i sat with my back against the door and put my legs against the wall incase my mom tried to get in. i would wait until late at night and smoke and i would count how many hits it would take me to get high i had such good times