Matsushima :
Yes I see. However, the 3350P combined with a cheaper non-overclocking chipset of course can provide similar performance, if the buyer has low money. I reckon it's possible to squeeze a Z68 and a 2500K these days under $600...
I agree the 2500K is the best bang for the buck compared to the 2600K and it was when I bought mine. However the 2600K is a little faster and I really liked the reviews and so so I spent the extra $80. The 2600K is just a great all around CPU. I think that the 2500K has dropped in price but it is still close to the same cost as the 3570K.
The advantage of the 2600K over the non-overclocking CPUs is that I can increase its speed and speed / power by 35% with very little effort. I have a gold-rated 850W PSU and a Noctua NH-D14 and so if I need more power all I have to do is overclock and it doesn't cost me a dime. In the long-term view this saves me money. Right now I just don't need the extra speed, but it is there and it is free if I need it.
Right now the 3570K is the 2500K of 1-1/2 years ago. It overclocks well and is at the $200 price range. Add to this that it is actually faster than the 2600K and it is just an incredible CPU. The advantages over the 3350P are many and the cost difference is not that much.
The CPU is not the best place to cut costs because you have the motherboard to consider. Sockets change and so forth. I think that the best place to cut costs can be found in the CPU cooler and case and other areas.
The CM Evo 212 does a competent cooling job and costs about $25-$30. The Corsair 300R case has almost all the bells and whistles of much more expensive cases and yet costs only $70 (after rebate).
For budget builders, I think these are the best places to save money. Let me say also, my heart goes out to the budget builders. It is tough to build a powerful computer on a limited budget and for many budget builders, this is their first computer build.