1. The "tap to call for assistance" feature doesn't work with paper.
2. You can cram a lot more information into an interactive screen than you can on a single side of paper -- the shop displays will be fundamentally more useful and informative.
3. Centrally controlled updates to pricing. Ability to request build-to-order options at the shop counter. Means less staff running around the store checking all the displays are in order.
4. When the iPads are out of date they can be sold off as refurbs. (They're embedded in plexiglass boxes so unlikely to get scratched up by customers.)
5. Power consumption of an iPad is dwarfed by the power consumption of the lighting and aircon/heating for that amount of floor space in a premium store.
6. These are probably minimum-spec 16Gb wifi-only iPads. (They're in a store, with guaranteed bandwidth and presumably a central server behind the magic curtain. They don't need to store stacks of movies and tutorials directly.)
7. Anyway, since when has "environmentally friendly" been a primary operational criterion for any high-end retailer? Apple aren't in the business of minimizing resource extraction, they're in the business of maximizing profits. Obviously, they think whizzy animated interactive store displays will help them do so. Saving trees is way down their list ...
