I'd say that while those auctions are worth a look, prices can get a bit silly because of the sheer numbers of people attending them.
Bargains can be had if you are willing or able to do some work on the bike you buy, just make sure you get to view the bikes before the auction starts.
Another option is your local Kierrätyskeskus, they set quite decent prices on bikes that are fully working when you buy them. Plus it is also possible to get bikes for free if, again, you are willing or able to fix them up yourself. I recently was allowed to scavenge parts from nearly 30 bikes that were going to be taken to the dump/metal waste centre. Most would have been easy fixer-uppers had i wanted another complete bike. Best part was that they said 'go take what you want'!
