I've worked with companies where we have pre-sold products (before they fully exist). By producing prototypes to get initial buy-in and then running pilots (trials) to get them to put money down.

These were potential solutions to problems that they don't have the budget or time to solve themselves

And what if it's a place for beta products looking for early adopters?

Same problem. Why would a business use a product that they don't know how long it's going to be around? They probably have to spend thousands of dollars to train their employees to use the new product, and if something changes (since it's beta), they need to again waste everyones time to explain the changes, and if the product goes under they have to find an alternative on short notice, and again train everyone...

I just don't see this happening, unless the new product has a massive value proposition...

So, how do B2B startups find their early adopters? Only through capital injections until they've a good enough product?