Ask HN: How do I price my SaaS web app?

I'm very close to an initial launch of a CRM app for not-for-profits, and my first two customers are asking for prices which I've been putting off for a while, focusing on the product.

I can't charge them a nominal fee until it's out of beta because they want to know they can afford the system before moving everything into it, so the pressure's on now!

Does anyone have any tips on how to best approach this, or how it's worked for you in the past? Is there a way I can figure these out that makes the most sense? My competitors are all old antiquated systems, I don't have a lot to compare to.