I understand your point when comparing both processors but it is important to say that both are completely different. The processor for the desktop system can deliver a huge processing power vs the cellphone processor. I am saying this because the phone processor is made for mobile systems and eventhough it is an octa core processor it cannot be compare with the desktop processor due to the design.
In many ways, the desktop processor is much better than a cellphone processor and this is where the price of the product will be visible.
No, there is no logic, at least in your example comparison. The MT6592M CPU of your smartphone uses an old Cortex-A7 cores, which are low-power, in-order architecture - thats why Mediatek was able to pack eight of such into one chip. Compare it to Atom line of Intel CPUs, where Atom x7-Z8700 have four out-of-order (more like i5 architecture) cores inside USD 35 chip, at same frequency as MTK chip. And yes, array of simple cores cannot be used well against complex, high-IPC CPUs, both in end-user and even many server tasks, what was clearly shown by histories of IBM Cell, Sun Niagara or AMD Bulldozer.