wow, I got my E8400 at the beginning of february for $209 shipped. i think $183 is Intel bulk price, right? so i think ~$200 is what they should be selling for now, assuming you can find one.
but supply/demand and all seems to be making the etailers a bit greedy.
as for the original debate, my gut feeling is that quad core still isn't worth the price/energy/heat premium for the majority of computer users. those who do serious amount of multi-threaded programming should probably consider quad if the price is competitive. but most users, gamers and even power users are just as well served by a faster dual-core that runs cooler, uses less energy and will match the performance of any quad in most programs.