It's time to face the fact that conferences are becoming antiquated by technology.
EDIT: Judging by the replies, apparently people think conferences are local get-togethers? The point of a conference used to be about exchanging ideas with people outside the neighborhood. It would roll in airline, hotel, $100s for attendence fees (because the venues are large and require organizers.)
Basically, these things turned into junkets in exotic locations. And then many companies decided they are no longer necessary in the age of the web.
So you can choose to quote your 50 euros and say that it's a conference, or you can examine how much money the "attendees from all over the world" paid in travel and hotel paid in and note that their money is now being substituted by the web.
Your call.
Much cheaper than an expensive conference.
Until technology can replicate that, I think conferences won't go away.
Holy moly, travel and hotels have gotten very cheap in Europe.
What then is left?