Like I mentioned earlier. What some DIY-ers do is buy Nicotine Base at the mg/ml level that they vape at and then just add some Flavoring and or Sweetener.
Not Recommending this company (although I have heard Good Things about them). Just posting it so you can get an Idea of cost of buying Nicotine Base in 6mg/ml
3mg/mL - 36mg/mL Nicotine Base - Nude Nicotine
Of course, you will need some Flavoring and or Sweetener. So for maybe 25 Bucks more you would have the Raw Ingredients to make about 500ml of Finished e-liquids in a Handful of different Flavors.
That's what I did for awhile when I first started DIY. I got my ready made base at EcigExpress:
1mg-24mg E-Liquid Nicotine - Unflavored Nicotine Bases - E-Liquid
They also have flavors from all the major flavor manufacturers and some of the lab ware you need. Doing it this way is a lot easier when you get started. A lot less mixing. All you need to do is add in your flavorings. And you'll still save a lot of money.