Property investment seminars are worth it for an advisory with a presenter people travel to see, a project where the room is the sales floor, or a database that needs waking. For most other firms, the room costs more per client than it looks. GoatedLeads sells a different kind of enquiry, so take this as a view from a supplier with a different product.
The case for the seminar is trust. An hour in a room with an adviser who knows the subject does more than any ad can. The investors who stay to talk afterwards are warm in a way no form can match. The case against is cost and timing. The advertising to fill the room, the adviser's evening, the staff at the door and the no shows are all real costs, and most never appear on an invoice. The follow up call comes a week later, once the investor has cooled.
So the honest answer is that seminars are worth it when the room itself is the product. They are a poor choice as the only way a firm finds clients, because they are a fixed cost with a variable result. The firms that get the most from them run events for reach and use per lead enquiries to keep the calendar full in between. If you have the presenter and the audience, keep the seminar. If you run one because the firm always has, count the whole month rather than the room.