Why the ecig market is a fucking GOLDMINE

I recently made my first purchase in the ecig world with a mechanical mod. If you don't know what that is it's basically this thing http://i.ytimg.com/vi/bxwJgZ4pCtc/hqdefault.jpg and they produce the most vapor out of anything in the ecig market. Now I don't like it at all and basically sold the thing in 2 days after I got it. Only until I sold it did I realize how much money you can really make off any ecig (or mods specifically)

Ecigs like these (mods) must be maintained. You have to constantly rebuild them, clean them out, and charge the batteries every 3-4 days, and also buy juices. You can get all of this done for a fairly cheap price, I'd say you could charge up to $10 for the rebuild/cleaning of the Mod. I'd say a weekly expense of somewhere around $20-$30 just to uphold a Mod. 

Now, I came to realize how easy it is to scheme on people in this market. The person I sold it to doesn't know anything about the market, and wants me to rebuild / charge her battery whenever she needs it done. She agreed to $5 a rebuild and $5 to charge it. She'll also need juices which I can get her a bottle for $5, but I'm charging her $10. So that's on avg $30 a week (one bottle a week, 2 rebuilds & charges) that I can make off of ONE PERSON. If I went out and got 2 more people mods I could easily make $90 a week simply doing these tasks for people.
 
Lets just take a minute to review what I'm making off of ONE PERSON.
 
I sold her a Mod + battery + atomizer for $90 
 
$90 + $30x = y
 
x = 4
 
$90 + $120 = y
 
Y = $210 / MONTH OFF ONE PERSON
 
Not bad as a little side project. If I REALLY pushed for this and get 5 people thats a little over A THOUSAND A MONTH from this. 
 
Now what I explained to you is basically what vape shops do to people. They do all of what I do but on a much larger scale. They probably get around 15-20 people a day coming in for rebuilds, and the juice prices are pretty ridiculous. They can set their own prices since there are no real regulations as of now, so they can easily prey on ignorance. Someone who knows nothing about ecigs can and will be tricked into overpaying over double the actual price for something. They've actually tried to do that to me, asking $115 for a $50 piece.

TL;DR Ecigs make money if you know what you're doing (also some bit about there being no regulations which makes for easy money)