Getting people to pay seminar attendance fees is not easy. But there are measures you can put in place, to raise the chances of getting people to actually pay to attend the seminar.
You are, for instance, more likely to get people willing to pay money to attend a seminar if you can demonstrate how attendance to the seminar is likely to lead to better career prospects.
You are also likely to get more people willing to pay to attend an educational seminar if you can demonstrate that the people who will be facilitating it (the resource people), are truly authorities in their fields.
At yet another level, you are likely to get more people willing to pay to attend an educational seminar if you can demonstrate that the seminar is likely to serve as a good networking forum.
You can demonstrate all these things through adverts placed in media. You can also sell the seminar on a one on one basis, by for instance, taking some time to sign up for a Ymail account, as per the instructions outlined in this site, and then using the account hence procured to send emails to people, telling them to attend the seminar and tactfully showing the advantages of doing so.