I dont really get whats the difference between a cheap transmitter and an expensive transmitter. I currently have the hpi tf-40. That transmitter responses fast and does its job. So why are these expensive transmitter so good.

I thought the same thing. I had an old school Spektrum DX3 and thought it was fine until I bought a MT-4. With the MT-4 I just felt way more connected to the car. You don't really release the difference in response time until you make the switch. Plus the features and functions of a quality transmitter can't be matched.

If youre just bashing and not racing then a lower quality radio probably won't matter but if you're racing you want the response time of a quality radio. Do you need a $500 radio? Nah probably not but a decent mid range radio will make a difference.

a more expensive radio usually has more features and better quality. multi model memory, faster frame rate, digital lcd screen, digital trims, adjustable servo speed, etc.

if you just bash 1 vehicle, a stock or cheap radio is fine but if you race or bash multiple vehicles, i'd suggest getting a better radio