Independent of the type of rocket is the launch means question. Some are planning a balloon launch. Surely, the cost of the balloon is to be part of the launch cost for N Prize cost calculation. Including the cost of the helium. Will it be possible to stay within the financial limit? Even if hydrogen is used?
If air launched, the cost of aircraft operation?
Maybe a concise definition of what constitutes a launcher is going to be needed.
For example, a balloon may have to be a part of the launcher if the high altitude is a requirement for the rocket, but a launch at sea might just be a launch location, and such a rocket could take off from a land based launch pad.
Charles Pooley (planning land or sea launch because I presently don't know which is easier to get the license for)