Well, it seems like the first to try would be Mikeusa, Vaporrenu and Vaporite. I still can't believe that prices may be that different. I would understand 20-30% difference but 3-4 times for the same stuff is just outrages.
Maybe it's worth creating a table with prices and the possibility to vote for quality. It will help to chose the best supplier and also create a healthy competition among them. There a lot of reviews in e-liquid section but too many and disorganized - hard to choose.