To understand drilling, you must understand parts of drilling. Most people see big oil rigs out in the ocean, yet those are just add-ons to support the actual drill and its functions.
1st. There are two types of drill bits, fixed cutter and roller cone bits. All current bits come from those types, the earliest bit was made in 1909, by Howard Huges Sr., the patent owner.
A simple overview of this information can be found here: http://www.ask.com/wiki/Well_drilling?o=2801&qsrc=999&ad=doubleDown&an=apn&ap=ask.com
2nd. There are diffrent types of drill bits for diffrent jobs, and the price varys depending on the job needed. To view some actual bits, check out these sites. http://www.rock-drill-bit.com/
If you are intrested in how the machinery work and how wells are drilled, look at these sites.