While searching price comparison sites FUD Zilla spotted you can now get a quad-core processor from AMD for a mere 99EUR. Unfortunately it's a Phenom X4 9600 2.3GHz with B2 stepping, you need to have a chip with B3 stepping to be free of the TLB bug.
If you want a quad-core from Intel you'll have to spend a bit more, the Q6600 costs 128EUR but that's not too bad considering you will need to get AMD's most expensive quad-core to match the performance of this chip.
AMD is the first to drop under the magic €100 mark, selling its Phenom X4 9600 for a mere €99. This is a B2 stepping 2.3GHz part, but nonetheless the price is impressive. For €25 less, you'll get one core less, as the X3 8450 clocked at 2.1GHz now costs just €73.90.
Intel is offering its legendary Q6600 for as little as €128 these days and the Q6700 for €158. If you're after new 45nm parts, you won't spend a fortune, either. The 2.5GHz Q9300 costs €185, while Intel's latest addition to its quad-core family, the Q8200, is listed at €177; but it will probably end up even cheaper once it becomes available.