How do you convince a hunter that the elephant he sees in front of him isn't a beast that he should try to kill? Speaking metaphorically of course.
I read a great blog post by Mark Suster a number of years ago which described the scenario of elephants, deer and rabbits. The analogy was to describe what kind of customer do you as a small startup try to tackle and the pitfalls you will inevitably fall into if you choose the wrong option.
The realities are that you have limited amounts of - well - everything.
The huge customer will in the end make you an indentured servant to their goals and needs.
There is really no way around it.
Avoid elephants. Deer rule.