Land is expensive. In Seattle, they already own a ton of land downtown. Not an issue there. In other cities I doubt it would be too hard to find some buildings

Land is expensive. In Seattle, they already own a ton of land downtown. Not an issue there. In other cities I doubt it would be too hard to find some buildings that would let them put a shipping container on the roof stocked with some essentials for a reasonable fee. Stocking stores is a solved problem in big cities. I don't expect a drone warehouse to carry more than a typical drugstore. They could even partner with local stores for order fulfillment. Remember, this doesn't have to scale out to all places and all items immediately. This could just start off as a way for tech hipsters in Seattle to order condoms on demand. If it becomes successful, they'll build it out as they need to.