Yep, the bargaining is the same as any other make. Maybe even worse, as many people buy a Ferrari but only keep it short-term, & then expect to get back what they paid for it. If they bought it from a dealer there is NO way they will get anything like that price when selling, even privately, unless the car is a short-supply new model.
The "20%" discount thing is meaningless. Many many owners don't monitor the resale prices of their cars & expect they have held their value (or increased), when usually the market price has dropped. This situation isn't helped by there not being many cars of a particular model around, so you can't just look in the ads & see (for example) 50 BMWs or Golfs of the same model to compare. There may be only 1 or 2 Ferraris of the model you want, so often the prices being asked are just way off.
Do as Senna says - look at market guides to get the real valuation range & talk to folks in Ferrari clubs & forums (like FF) to determine what you should pay for what quality. Then check the cars on-sale. Unlike Fords, etc, you will often find a big variation in prices asked (again due to vendor "ignorance").
A lot of it is "educating the seller" to lower his/her expectations - tell HIM what the market price is & show him how you have established that (market guides, valuations, insurance values, previous sales, etc). Ask him/her why he thinks the car is worth what is being asked (most just say "I think it is" - doh!). Most of all look at LOTS of cars & don't fall for the first one. You will very soon become much more an expert than most sellers & you will be able to set the right price in your head after a quick inspection. Your $55,000 car may be excellent buying at $52k, or maybe worth only $40k - you have to find this out.
And as mentioned, always pay for an expert inspection before parting with your money & make this part of the terms - you don't want to end up with a problem Ferrari !!!!!
Good luck.