Whenever possible I buy direct from the manufacturer. Any shop that claims to sell a flavor for less than the manufacturer of that flavor charges is probably watering it down or selling a cheaper alternative that is posing as the real thing.
Unfortunately I can't do that with FlavourArt since they are based in the EU. I suppose I could, but the shipping, customs, and money conversion is a major expense, hassle, and long wait. But for companies like The Flavor Apprentice, I buy directly from them.