A stock gen2 motor is capable of low 9's in the 1/4 mile(maybe more). That depends heavily upon the rider's size, skill, track conditions, air temp, wind, ect. That's usually strapped and stetched too.
If you want to go really fast you're looking at a big shot of nitros or a turbo, and there's a handful of guys running superchargers. All of these engines need built to handle them... or they will be after a few passes.
These bikes are also stripped of any excess weight and most in the video have alot of high dollar parts. Even plastics are very expensive.
A stock gen2 is capable of getting into the 9's in the 1/4(again, alot of things determine that). You can get a front end strap(for lowering)and extensions that bolt to a stock swingarm, both are fairly inexpensive and will help improve your times.
There is alot involved in going that fast, and doing it consistantly. There are also alot of guys here that do that, and can give you advice on how and where to start.
Just remember the old question. How do you make a small fortune racing? Start out with a big one!
You can have dragracing fun pretty cheap, but the guys in the video are serious contenders and big spenders! They have more in mods than the cost of their bikes, some of them several times over.