COA for Supplements- ballpark cost

Hello, I’m in the process of launching a supplement brand for sale on Amazon first. I have been reading up on needing a COA. I have reached out to a couple of ISO 17025 certified labs but haven’t heard back yet. Wondering if you guys have a cost estimate I can expect to pay for this certification per product? After Amazon sees the trademark and brand info I’ve submitted at what point do they require the COA? Is it before or after you get a shipping address to send the products to their warehouse?