All my answers to this are variations on 'know your target'. In response to the people above who say that you should get what your time is worth, I would have to say, get what your customers time is worth. Or even better, get what they think their time is worth. They may consider your product to be a lot more valuable than your own estimation. Experts sometimes don't realise their full worth, although that's not usually a problem in IT.

By this I mean that it may have taken you months to write, but maybe it could save the customer a year of work, or perhaps they could fire someone and replace them with your product. Then it would be worth paying you much more for one license than you would have got for your time programming it at normal rates.

Since you haven't mentioned any competing products (or their prices) your product may be unique. In that case you would have to try and hang out with your target market somehow - online or in the real world.

Perhaps you could cut a deal with a publishing house, or a marketer who has relevent experience. A twenty percent cut sounds high but if he doubles your sales, well... you are still ahead.

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Jeremy
I didn't believe in evil until I dated it.