I think that your prices are too low. For why, see John's good write up here:
http://www.internet-marketing-blog.c...stige-pricing/
Frankly, if you're going to promote your directory seriously, I'd charge *double* what you're suggesting. And really use the extra money to build the directory.
(P.S. If you start with the higher prices, a lot of people will be unhappy, but they probably are not your target market anyhow).
Good luck with your directory! I'm sure it'll be a success.