Seminars and Webinars are AWESOME! I love the education they provide, but as a business developer and marketer, events are measuring tools. They tell you exactly who is ready for the follow up conversation.
The best way to promote your webinar or seminar is with LinkedIn Events. DO NOT spend $8000-$10000 to promote a webinar to someone else's network. You spend money to nurture their network with the hope of landing 3 meetings. Sounds like it is good for them and you get to feed a bunch of plate-lickers. What a crap shoot and a waste of money.
LinkedIn Events (and email if you've been building your email database effectively) is the best promotion tool you have. You can do it for free or we can do it for you.....at about 5% the cost of the other guys.