As much as I would like to support the YC startup AirBnB, with a quick search on hostels.com I found a bed for €13/night. A similar bed on AirBnB costs €20/night. I'm not sure what price I can achieve if I find a private room that allows me to split the price with others.
Thanks for the referral. The $25 credit only applies (to me or you) when I book something with over a $75 base rate. So you won't get it today but next time I go on vacation for longer you will get it.