[notacoward]

There's a problem with the word "customer" here. Sure, having a large customer - i.e. somebody who has paid or is paying you - is fantastic in all the ways you mention. Unfortunately, what the OP was really talking about was prospects. People who dangle hopes or promises of some huge future gain, but with the condition that you have to expend a great deal of your own resources and use up your own runway to collect, are not so beneficial. They're the Nigerian email scam of business strategy.

"Greetings, X. I have many millions of dollars I'd like to spend, and I'm willing to give you a share. To facilitate this, you need only devote 50% of your company to me for a year. Please start working on features Y and Z immediately, so that I can make you rich."

Yeeeeaaaahhhh, not so much.