You can also try just using the scotch tape over one lens, makes it fuzzy which takes the pressure off your eyes/brain to converge the two images, yet leaves you with some sense of what you're seeing and peripheral vision.
Why do they HAVE to use high index to add a prism? How much prism is it? I have had prisms made in regular plastic lenses. I cannot tolerate the high index material, nor polycarbonate, nor any change in the base curve of my lenses, nor anything (I am the original Princess and the Pea). And the lenses should not be so much more expensive. The eyeglass chains, especially, push the fancier materials at insane cost. We go through our local optometrists, two different ones, and the fancy lenses, even polycarbonate, cost the same if not slightly less than standard plastic, because they are not out to gouge their patients (their frames, however, do cost more, but most will let you bring your own frames in).
Put the order on hold, shop around because you should not lose your house over lenses, and meanwhile try covering or taping over one eye/lens.
But the depth perception thing when only one-eyed is very real, so if you cannot avoid driving, the glasses are a better bet.