Ok, think gumball, but on a TIGHT budget and you are along the right lines.
Cost is 100 quid per team to enter (if you are early enough, it gets dearer the later you are to enter).
Car cost = 100 quid
Petrol cost = 300 quid (ish)
4 day event, ending in Naples in Italy.
Basically you buy a car for no more than 100 quid, then you drive it over a period of 4 days racing to italy, the winning team gets a grand as prize money.
Then you check the car into the long term stay car park at the airport, and abandon it forever there and fly home without it
Teams can have as many or as few people as you want i believe.
More info here: