According to the Low - to - High price range on the site, Evolved Novelties Toy Lube
is the cheapest right now, and it has a decent overall rating and a few helpful reviews.
Always check the volume of the container before you order. Sometimes you can get 2x or 4x (or more) the lube for just a buck or two extra.
Also, you might want to look into joining the Eden Fantasys review program (details under your account settings); once you get that set up, you could order sample products to try out for free, in exchange for writing a detailed review. There always seem to be some new lubes available.