If going straight to manufacture in factories is too expensive, you may end up in the chasm between prototype and mass production, where you have demand, but in low quantities, and you can't afford the tooling or assembly line setup or to meet a factory minimum order quantity. At this point you have to get creative and figure out how to manufacture them yourself for as cheap as possible with as high a quality as you can get. This is tricky, but if you can do it, then you can cross that chasm and use your sales as leverage for investment in growth. It will also teach you how you can refine the product for easier and cheaper and faster assembly, and you will end up saving money when you do go to a manufacturer because you will have worked out many of the kinks that can delay a new assembly line.