The 1.6L is mostly exclusive to Singapore because of the tax savings (THERE), I'm not sure what other countries it is sold in.
I do know one thing- the fuel economy of the 1.6L and 1.8L is the same; so again whats the point? My "reborn" gives the same mileage that my 1.6L 02, 04 Vtis give (11-12km/l in the City, manual transmission). From what I've read about the R16, its got lesser torque/hp, makes the car feel a bit underpowered and has the same fuel economy.
The price difference in the engines (R16 / 18) would be nominal, its only a matter of smaller bore and stroke, the engine is technically the same. So the cost saving would be minimal as well. I believe Honda is giving consumers a better saving by only having 1 engine.