I’m more sceptical of the 82 days than of the price bracket. Visible listing time does not necessarily capture earlier marketing, withdrawals or a relaunch at a lower price. Before linking speed to energy performance, trace the listing history and note when the first price reduction happened.
Capacity matters if people are bringing detailed questions. A smaller room may be cheaper, but it becomes awkward when unconfirmed attendees arrive. A simple RSVP deadline plus a waiting list would give you a better number before committing to a venue.