[pa7x1]

You seem to argue from an economic point of view, as if it was too "expensive" or "wasteful" to have all those universes. But MWI doesn't add any postulates to QM, in fact it is the simplest of the interpretations and a direct translation of what the math of QM says. All those universes are as "expensive" as the quantum mechanical state superposition they represent, and the superposition is a central tenet of QM and thoroughly tested. Your conclusion could be rephrased as "quantum superposition is fun but absurd".