The catch is the part just above. You're comparing the purchase of 18,000 mg (36 mg/ml * 500ml) to 50,000 mg (100mg/ml * 500ml) -- and nicotine is cheaper the more you buy. However, to make a set amount, you would instead purchase roughly 1/3 the amount of 100mg vs. 36mg. And, when you do this, cost differences largely disappear. If you'll note in my example (48ml vs. 100ml), the purchase amount of 48ml is twice that of 100ml. I'll post cost comparison of 36mg vs 100mg hopely later this weekend. Cheers!
Honestly, I don't get it. When I buy nic, I use it all. If I buy 50,000 mg of nic at .11 cents/mg it's going to cost ~$55. If I buy 50,000 mg of nic at .16 cents/mg it's going to cost me ~$80. And the cost of the VG and pg don't make enough difference to change it (for me at least). Anyway, I look forward to reading your comparison, maybe that will clear it up for me.
Either way, my original point was that the cost savings aren't that significant (although I still think they do exist).