Welcome! Vienna is here.
I buy my wood from
www.muehlbauerholz.com. It is not particular cheap. Here they have a link to
Preisliste Schnittholz PDF that has the prices. But they also have some exotic timber. I mostly buy beech (Buche) and it costs now slightly more than 1 EUR per 1 kg.
Also I came across one German woodworking magazine and they have a list of places
where to buy wood (Germany and Austria though).
But I always wondered is there any place in Slovakia near Vienna as it might be cheaper there. Let me know if you find something