What price increase are you referring to? The fluff one? The Dustoff is the same price and availability in both SR4A & SR5. (12,000Y & 10R)
Unless you meant keeping it's stats locked behind Bullets & Bandages when Rigger 5.0 specifically mentioned it?
The Dustoff is a Large VTOL Drone with a built-in Valkyrie Module. As a Med-Evac/Personal Chopper it's designed to carry a metahuman. As you say other options would require GM approval.
If you wanted to add a Rigger Cocoon or Valkyrie Module to another drone, the only other Large Aerial Drone is the Dalmation. Which would then cost (almost) the same as the Dustoff. Admittedly with small stat differences. Fine by me.
If you went for a non-Aerial Large Drone or any vehicle, it would cost you (Body x 3,000Y) for the Rotor mod plus the base cost of the drone and the Cocoon/Module. It would just be cheaper (and require the same licences) to buy the Dustoff.