I beleive it is far cheaper to DIY. My recent calculations has me at $.13 per ML, please bear in mind, I am at 8MG strenght, even 24MG would be under $.50/ml
Startup cost really isnt that bad. All you really need is dropper bottles ($.79/ea for 2dram size), rubber gloves and pipettes for transferring liquid. My Original start up costs (equipment) was under $20
For materials, I use 100MG base liquid that I get for $99 for 250ML, at 8MG strength and consuming 5ML per day, that is almost a 2 year supply. PG or VG is fairly inexpensive (make sure it is USP)as well. Many can find it locally, I just get it from online vendors. Flavoring was the key, I did not like Loranns oils very much or capellas flavorings. What I did find is that I LOVE Decadent Vapours, which is sold over at TW (Totally Wicked).
Putting the mixes together is not any more complicated that being able to count drops. You have 3 basic ingredients, liquid nic, flavoring and a dilutent. You count the drops of the 3 to make the mix. You DO want to be careful and respectful of the liquid nic power. As long as you are not reckless or sloppy about it (I make my mixes in my kitchen sink) you can be very safe.
O.k. now for some linkage:
Here is where I got all of my supplies:
2dram plastic bottles, latex gloves, syringes, pipettes and PG/VG are all priced nicely at:
http://www.ecigexpress.com/diy-supplies-c-3
Liquid Nicotine is purchased here, I can state from experience that the quality of the liquid is very good:
http://myfreedomsmokes.com/diy.html
Finally, the flavorings:
The native site of the supplier (not a store) is:
http://www.be9.net/decadentvapours/flavours.htm
(favorite flavors include; apple pie, cafe brasiliano, french apple tart, Strawberry tart, Tiramisu, Choc o Mint, Mentholyptus and Sour Cherry)
These can be purchased at Totally Wicked
http://www.totallywicked-eliquid.com/products/e-liquid-flavourings/decadent-vapours-10ml-flavour-2-product.html
(this British company ships out of the US so dont let the funny accents and bad teeth fool you)
And finally, you need to create the recipes to make your mixes. There are many but I use this one:
http://www.tji-java-ide.com/e-cigarette/index.php?option=com_wrapper&view=wrapper&Itemid=88
You can save your recipes, which is handy. You will see one towards the bottom called: "Decadent Vapors (Any Flavor) by Burn". That is my base recipe that I use, I created it when I was at 12 MG strength.
Whomever starts mixing their own, enjoy. Fresh juice, ability to customize and cost will all be benefits you will enjoy when creating your own.