One goggle - two lens! Gives you a choice.
ALL goggles have replaceable lens. But only a few goggles have interchangeable lens
. So what's the difference? A replaceable lens is only designed to be changed when the one that came with the goggle is damaged. These lens can take up to 5 minutes to exchange a new lens and many times never seal as well as the original lens that came with the goggle.
Goggles with interchangeable lens means the goggle comes with two (or more) lens and is designed so you can interchange the lens easily and quickly. Sometimes less than 10 seconds. So on sunny days you put the dark tint lens in. On cloudy days, you put the light tint lens in. The extra lens usually comes with a storage bag so you can carry it on the slopes.
If you believe goggles with interchangeable lens are too expensive, you need to remember the lens is the most expensive component of the goggle and you're getting two.