Undeveloped land is still taxed at a higher rate than developed land. There is also a "speculation" tax. Most people I know don't qualify in the speculation bracket so the tax isn't a well known one. However this is the reason why many larger tract land owners on the mainland converted their lands into nature reserves - so that the speculation tax would no longer be a burden.

Really if you look at the stamp duty on real estate as a "one time" tax then it isn't as painful. If you were to analyse the taxes payable on land transfers in the US you would see that the 5% of the purchase price tax is on par with many of the accumulated US taxes. By the time you factor in origination fees, county, state and federal taxes what do you come up with? And then crippling annual property taxes thereafter.