Selling a Car in Spain - how does it work ?

[ESDavey]

I want to sell my Spanish car to a colleague at work. I've been told that there is an agency that can do this but charges :

Traffic + agency fees = €159 + 4% €500 appraisal value of vehicle = €660 !!!

I cant believe Jose Spaniard pays this amount of money just to transfer ownership of a car. DVLA does this for free !!

Can anyone clarify the process please ? Thanks