It really depends on the manufacturer. Some don't want to deal with you unless you're in the 100s of thousands. We were very lucky to find a company that will make a quantity as low as 300, but there would be no reasonable price we could charge for the product without losing tons of money. A quantity of 3,000 would basically be a wash, and 30,000 would give us a decent margin.
Another point I forgot to mention above is assembly cost. I was surprised to learn that automating tasks isn't cost effective even when production is in the tens of thousands (depending on the task of course).
