I just came from Central Europe and agree that the budget is too low IF you are used to traveling a certain way and IF you are older. I'm a 56 year old woman who has traveled a ton and when I first started at the tender age of 19 I did the hostel thing, camping, and any other cheap way to go. But now, I'm not into that as much.
I agree with others - the transportation costs can add up quick. But there's tricks, like hopping on and off the bus before they collect your ticket (I"m only sharing this because this is what the locals told me to do - but I did buy a ticket anyway). Or walking everywhere, which does limit you but then there's bikes you can rent.
Trains, planes and buses were more expensive than I thought and quickly ate away at my budget. I couldn't seem to save on any of them. However, I did learn that lots of folks drive to different locations and if you can find a local heading that way (usually on the weekends) you can hitch a ride and share on just some expenses or at least buy a bottle of wine!