If you're actually interested in the product, the best policy is to just reply with whatever answers thay are expecting - high volumes etc. Make up a potential product if necessary, and tell them you're a consultant/contract design house and can't give details of the end client yet due to client confidentiality, and for the same reason don't know about markets, production schedules etc. As regards NDAs, a few 'errors' in things like name, address etc. easily render them meaningless.
Although it's a PITA, it also doesn't make sense to just look elsewhere as you may be missing out on something useful.
Think of it as a first-level timewaster filter and play along to get what you want regardless of their dumb policies.
Just tell them what they want to hear - you can always tell them things didn't work out later if they follow up with volume sales enquiries.