1/2 the price of the E8400, the main difference is that it has reduced 2MB L2 cache, compared to 6MB on the E8400. This will make it 5 - 10% slower per clock in general, but at $90 its hard to beat from a price/performance POV, especially since previews have had it overclocking to 4GHz.
epsilon has a good point. The e5200 has a fsb of 200 which is quite low and a multiplier of 12.5 which is, looking at the other core chips, insane. Considering the price theres nothing that can go wrong by buying it.