On the juice source... I think MyFreedomSmokes.com has about the cheapest nic concentrate that is frequently talked about and reviewed here. They charge $50/liter of 100mg concentrate. From time to time they sell it for $40 on special and I picked up a liter the last time they did that. I've seen nic as high as $100 for the same one liter/100mg concentrate. I have only bought mine from MFS. I was happy with it and I figured ignorance is bliss
There are some huge threads here comparing various nics. Seems to be a very personal choice, so if you are picky, it might pay to order some small or sample sizes of a few different vendors to see if a "premium price" nic is worth it.
I figured my cost, based on $50/liter, at something like 2 cents to 2.5 cents per milliliter, factoring in MFS's price on PG/VG. That's about $0.60 to $0.75 for a 30 ml bottle. Even with $100/liter nic that is less than $1.50/oz or 30ml.