USBasp is an ICSP (In Circuit Serial Programming) adapter that allows you to upload firmwares and install bootloaders on common AVR microcontrollers. Insted of using Serial port or parallel port this programmer uses USB port. The USB interface is achieved by using an atmega8 and the rest is done in firmware. Being an Open source hardware project, released under the GNU General Public License, you are free to download the schematic and firmware from Thomas's website.
If you go with original USB Programmer from Atmel like AVRISP-mkii It will cost you near about ₹4000 and its very hard to find here in India. But you can easily grab USBasp in less than ₹300.
If you are good at hardware you can make it own in less then ₹100. But you need a working programmer to make a new programmer (Sounds like egg hen story )