Epoxy manufacturers make many epoxies not all of which are designed for a transparent lay-up. If price is your first concern, the cheap epoxy may not be optimal for a transparent lay-up. A fast setting epoxy will allow less time for bubbles to rise and dissipate. Using warm temperatures to thin a regular viscosity, fast setting epoxy (MAS), will not allow bubbles to rise and dissipate as well as a regular viscosity, slow setting resin (System Three).

Um.... At $100 a mixed gallon I wouldn't exactly call Super Sap a "cheap" epoxy. It's a well-respected bio-based resin that is used by numerous composite manufactures (mostly surfboards, longboards and snowbaords. Check out their partners page). I also use it exclusively in my own commercial shop. It has very little odor, wets out tight weave cloth beautifully, it's easy to work with and is bio-based. Nice stuff.