@liudr, Digikey sell the bare chip for $7: http://parts.digikey.co.uk/1/1/822588-ic-mcu-avr-64k-flash-40-dip-atmega644p-20pu.html
Wulfden sell the chip with bootloader, socket, crystal, caps and reset switch for $11
http://www.wulfden.org/TheShoppe/freeduino/rbfk.shtml
But if you need USB then the teensy may be the better choice.