I think Italy is doing this as a straight attempt to raise money from what they perceive are tax evaders.
The news here is full of anecdotes about e.g. the tax people "visiting" some event where there were 100 Ferraris, and nobody present was declaring more than 10k in income - or some [insert your own figures] variation of that. Same with luxury boats. And I am sure it is true. In Italy, and even more so in Greece, more or less the only people who pay anywhere near all taxes due are ones working for big companies who thus cannot avoid paying income tax. Most people involved in say tourist trade, and most self employed (doctors, etc) run in an essentially cash world.
And with the economic storm going on here, everybody who can get Euro cash is stuffing it under a matress, or into Swiss banks, while they can, because of their country dumps the Euro and prints Liras, Pesetas or Drachmas, the Euro bills will be the only currency worth having. So things are getting worse for tax collection, not better. The difference, apparently, is that Greece is not so stupid so as to kill upmarket tourism (I flew there
last Sept and had no issues beyond the usual) whereas Italy has proved to be more stupid than absolutely anybody would have believed.
I know Italian (or of Italian descent) pilots, living ouside Italy, who have been staunch supporters of Italy and the Italian way of doing things (OK if you live there, speak Italian, and have the right contacts
) and none of them will even fly into its airspace now. The cost of a screwup is way too high now.
There are well documented stories of somebody landing at say Luxor (Egypt) and getting fleeced of US$2000 before they would sell him fuel. One kind of expects this in Africa, and ferry pilots who go there tend to carry copious amounts of US$ cash, but nobody expected Italy to do extortion on such a scale.
What Greece did with private aircraft is quite cunning. A particular type, say a TB20, is assigned an "income equivalent" of say 150k euros. If you are declaring that income, you pay nothing extra. If you are declaring income of say 70k euros, then you get taxed (at some rate) on the 80k shortfall. Workarounds include forming a syndicate of multiple owners, or registering the aircraft in another country (with Bulgaria, or the USA, being popular, but they have their drawbacks).