With ED's current sale 2 Glycubes plus $46 shipping is only $16 - $17 per gallon average, still a really good deal. I only buy in bulk and only when on-sale but I also factor in shipping costs when comparison shopping. For PG and VG I've purchased from Essential Depot
(great products) but last time around found a better deal at Bulk Apothecary
Natural Ingredients and Raw Chemicals Two weeks ago Bulk Apothecary ran a sale on USP Kosher VG, 50lbs
(aprox 4.75 gallons) for $39
(~$8.25 per gallon). I didn't need any and the sale is now over but the last time I purchased from them the shipping costs
(to me) for 50lbs was $23 by FedEx ground which would bring the
true cost per gallon between $12 - $13, what most DIY'ers pay for a single liter. In the past, the period between Thanksgiving and New Years eve was usually the best time of year to watch/buy. With so many people rushing out to buy DIY supplies I don't know if the sales this year will be as good, supply and demand you know.