Regarding the pricing, first I'd like to state again:
Yes. We are currently talking to wikimedia as well as soundcloud and see about availability of their spaces.
I think there is a misunderstanding here what this event is doing: it is a one-time evening events with 15 lightning talks. There won't be any training on side, nor do we ask from anyone more than 5 minutes of their time presenting their projects, which is very much in their self-interest.
Many companies and cowos (including beta-house and co.up) give their spaces for such an event for free. Depending on the sponsors, we (as HS, as OTS in Berlin but also at other places) also did have food occasionally at these kind of events in the past – we haven't advertised with that necessarily, but Soundcloud, Zalando and Wikimedia do sponsor food for that kinda stuff on a regular basis (mostly Pizza or sandwiches though, which we want to change, too).
Of course you are free to bring your own food and drinks, but it is also just nice if you can chat with people while having drink and eating stuff. Especially for connecting with people this is so much more effective – why do you think conferences take so much care about this kinda stuff? And connecting these people is the exact purpose of the event. Hence: providing food and drinks is really helping the cause a lot here.
I'd like to reiterate nicolai here:
I think that is very important. At the same time I very much agree with @rachel that there are things that cost money. No one has any intention to actually pay anyones work for this, that wouldn't cover any costs what so ever. But asking for a donation, giving a recommendation on what the organisation thinks is appropriate, reminds people that things cost money – and gives them a very convenient way to support he organisation behind it. And let's face it, we are organising events for a highly paid and very privileged part of society. Asking them to chip in, so that OTS in return can print stickers to promote its events more – to the parts of the society it tries to include – is not a bad thing.
I am also hoping by stating that donation price – even if you can put it down to 0EUR – that people stop for a moment and think if they are actually gonna come. I hate to organise events, where we had to turn down sooooo many people and still have so much more space available because too many people just "secured themselves a space in case they might want to go" – and clicked the button without ever thinking about it (hence the reason I didn't put this event on Facebook or Meetup).
Will that work? I have no idea. That's the point of an experiment after all: to learn from it.