1. Raspberry Pi Trading use UK based manufacturing facilities, so yes, it costs a little extra to ship outside of the UK.
2. Raspberry Pi Trading do not have the capital to make x million devices upfront. So supply will always be limited for devices like the Zero, while demand is high.
3. The profits from the sales of all Raspberry Pi devices are used to fund the Raspberry Pi Foundation. We do charitable work to further Computer Science education around the world. The target audience is educators and children, and that will always be the focus. That it happens there are hackers out there that want to use the device is great, but not the priority.
4. The popularity of the Raspberry Pi range is mainly down to the amazing community we have and the huge support available from that community.