My girlfriend and I are going to YAPC::Eu in Vienna. We're taking the opportunity to see the city so I've booked the plane tickets with a day to spare before and after the conference.. The flight details:
Mon 27 Aug 2007: Brussels-National (BRU) to Vienna (VIE) [09:10 - 11:00]
Sat 01 Sep 2007: Vienna (VIE) to Brussels-National (BRU) [06:50 - 08:40]
The fare itself costs about 10 euros, taxes are a killer 116 euros. All things considering, that's a very cheap flight (two people, two way). I'm guessing the accommodation will cost us more than that.
You might want to add your flight information to our Wiki. And yes, accomodation will be more expensive than your flight, unless you choose one of the youth hostels listed here.