There are some funny Americans here!
For example Audi TT has a base model with a 1.8l TFSI engine and 160 PS.
Mercedes SLK has a base model with a 1.8l engine and 184 PS.
In some countries these base models are enough because the taxes for the engines with a capacity over 2l are quite high!
Adding an M Pack, S Line, etc offers a more aggressive look and a sportier drive and again this is what a lot of young persons want!
Base price for Z4 20i in Germany:36.600 Euro ~ 47300 $; in US the base price for Z4 28i: 48650 $.
If we take into account the fuel prices you will understand why the Europeans like these base engines too