Hrmm, I got 3 opteron 165's right now all over 3Ghz with no problem.
Bought all 3 cpu's for $60ish used. I had my original DFI mobo when it came out and I bought for $125 but the other 2 boards I picked up for $50 used. 2GB of DDR memory capable of 250+ FSB can still be had for about $80.
If being frugle and going used like I did, that's 60 + 50 + 70 = $190 for a pretty sweet setup. IF talking retail prices this is more like $100 for the chip, $60 for the board and $90 for the memory. So about $250 in retail terms.
People already posted the prices for a "comparable" intel setup.
E2xxx cpu setup for about the same price considering that DDR 2 is cheaper but the boards a tad more expensive.
So is an overclocked 3Ghz E2xxx setup really much faster than a opteron 165 at 3Ghz with the same amount of memory for both? Yes, but is it by a large margin ? less than 1% to 5% really. So if you already HAVE a skt 939 mobo and memory, switching to the "cheap" intel setup isn't worth it in my book.
Now, do I think if you are building from scratch that the "retail" prices for building a cheap AMD system is worth it? No. If you don't already have some DDR memory, and good memory, I wouldn't bother. Go with a cheap intel if you are worried about price as you'll get a tad more performance for roughly the same price. If you are worried about performance then Intel at this point is definitely better but the prices start ramping up fast for Intel.
So in conclusion to what I said above, if you already HAVE a good skt 939 setup but with a single core and are looking to breathe more life into your rig for a few more years, this is an excellent deal. If not, it is not.