In terms of how much to charge: look at the value you're providing. Look at how much customers are spending on alternative solutions. Even if there's no product that solves the same problem, they are likely solving it somehow. If it's by doing manual work, try to estimate how many hours. And how much they value their time (e.g. how much are they paying for other things that save them time)

It's also a matter of just testing a bunch. I find it easier to start low and keep increasing until you hit diminishing returns.

Doing it the other way around (starting high) tends to be trickier as you'll end up with a bunch of early customers who feel they overpaid.