How much would your charge....

I've got a niche market that I've sold a few software products to.

I just developed an invoicing, estimating, payables, contact manager product.
Something they have told me they wanted.

Its a basic software solution that will allow a business owner to run their business. Nothing too fancy. Just geared towards their industry.

NOW... there is tons of software out there for free that will do 80% of what they need. So my question is how much?

$10,$20 or more?

Its four modules that are geared towards their industry. I'm thinking in the
$10 to $20 dollar range. I've put a lot of time and effort in to getting this thing up and going. Maybe I'm too cheap?


Any thougths?