The "new" road tax scheme was introduced 2009 (some say because of the flood of japanese imports) and is based on horsepower, emissions etc etc ... I also do not know the details, you can find all on homepage from Transport Malta (or google it).
But for all cars made after 2009 or have been imported to and registered in Malta after 2009 (take a look at the logbook) the annual road tax is much higher now (in some cases up to 4 or 5 times) and is increasing in steps every year.
Therefore the price of all used (old) cars built/imported before 2009 increased a lot.
Watch out for terms like "old tax sheme", "old licence", "old road tax", etc.) in the classifieds. On the other hand "Imported from UK" means you have to add a lot of money to get it registered here !
Other issue is the "registration tax". You have to pay approx. 35% of the current vehicle value to get it registered in Malta (there are some exeptions ...)
So, because of the registration tax I sold my Mitsubishi 2003, 90.000km, 98HP, 1600cc with aircon in very good condition etc. in Austria for 2000,- and bought an old Avella 1999, 130.000km, 75HP, 1300cc with aircon in quite used condition at 3000,- (prices in summer are also much higher than the rest of the year) ... but the good thing is, that I have to pay only about 150,- (or something) per year for insurance and road tax instead of about 400,- or more for a newer car with similar engine.
And also take care of the VRT date (vehicle roadworthy test), especially for old cars ! If you buy a "bargain"
that needs to renew the VRT in a few months it's possible you have to spent lots of money in repairing and parts.
I learned that there are following "conditions" for used cars (below approx. 5000,-):
* "in perfect condition" - means the car is OK (exept shocks, gearbox and steering
)
* "in mint condition" - means the car is still OK, more or less, anyhow, your expectations should not be too high 
* "in good condition" - means the car is already very much used (like mine) and needs litte attention here and there, but it is driving 
* "without any description" - drive it as long as you can and then sell it to a scrap company 
Always keep in mind: the cars in Malta are used at low speed (1/ 2/3rd and reverse gear), the steering mechanism is highly stressed, also the springs and shocks. Because of the sun all plastic/rubber/textile parts are aging very fast ... and the cars are mainly used for very short distances (which is deadly to diesel engines ... look at the black smoke coming out from not soo old diesel cars).