You need to find out if your customers not only like your idea but are also willing to pay for it.
Do not rely on promises. Get your customers as close to buying your product as possible without actually manufacturing it. Try the methods below:
Before building your product you can advertise it through a landing page and measure how long people stay on the page, what they look at and also if they register to be informed about product launch etc.
A price calculator helps you and your customers to understand the pricing model of your value proposition. It can be used to test different pricing models and to understand which aspects of your product add the most value for your customers.
A letter of intent is a signed document in which a potential customer (usually a B2B customer) states its interest in buying your product once it is launched. The document is quite precise in regards to features, quality standards and price.
Pre-ordering means that customers pay you before you started production. This can be a great way to actually finance the production costs. You can collect pre-orders through your website or a crowdfunding campaign.