well I am looking at this from the other side, I am trawling the net to add my new website to directories to try and improve it's pr.
Because I am limited to time and a very tight budget any site that asks for payment without a high pr of 4 or above I ignore and move to the next one at the moment.
Here is a good example of making it a pay site too early?
Qango : Entertainment: Music
The PR of the previous page is 4 but look hopw few people have actually added their sites.