Regular Kilz has a lower amount of solids in the formulation than BIN primer, hence the BIN is more expensive. The same is true for paints: the cheaper paints are thinner and have less solids. Kilz does make a "High Solids Kilz" which would probably be equivalent to the BIN, in both price and performance. As far as primers go, a lot depends on what you're using it for. Zinsser products (BIN) bond exceptionally well to glossy surfaces and have excellent mildew resistence. However, neither of these products should be used as exterior primers on bare wood, as they get brittle and will fail, unless used solely as a spot primer. Make sure the application you're using it for matches the product.