I have an entry level Gaggia (I forget what type, but it was about $200), and while its body is plastic, its guts are pure metal.
That being said, I think I have gunked it up using hard water. It doesn't pump as well as it did when it was new. I just cannot get the stream of espresso I used to.
To be honest, I really like the espresso from stove-top pots.
Cheers,
Chris