[chris lewis]

You are correct - historically Roof binos like the Meade 9x63's are more expensive for the reasons you outlined. A general rule of thumb is, you will get "more" binocular for your money in a porro prism, than in a roof prism costing the "same" amount. It is generally understood that it costs more money to produce and manufacture roof prism binoculars. The Chinese labor market is starting to change this however.
Porro prisms also inherently produce a brighter image as less light is absorbed then their roof eqivalents - although this is changing with phase coatings on the roofs.
Sometimes it come down to preference - 'birders' do prefer the more compact roof designs for instance - ergonomically also some astro observers prefer roofs as they are slimer to hold.
Roofs can only go up to 15x due to there inherent inability to exceed your inter pupil distance - as they are two 'straight' tubes. You willl never see a giant 'roof'.
There is an ongoing 'roof vs. porro' debate - much like Newt. vs. refractor.
In the end the consumer wins with more choices.