They're busy trying to make a living and can't afford to spend hours with you in rambling discussions. If you're worried about disclosing proprietary data to them, most contract manufacturers will sign a non-disclosure agreement. Suitable forms can be found in most inventor books. If you're going to ask that such an agreement be signed, be sure to verify that they will before setting up a meeting. My own personal opinion is that such agreements are generally an unnecessary hassle and impediment to doing business with contract manufacturers.
Contract manufacturers sell manufacturing services .
Then take that inventory out, sell it, and use your proceeds to go back and buy more. I've seen inventors talk contract manufacturers into doing their tooling and initial inventory on nothing more than a promise to buy from them for a couple of years. And everywhere in between. Recognize that contract manufacturing is a service business. During a downswing, it literally costs them nothing more than raw materials to do your tooling and initial inventory.