There's a very good sibling answer. Something that I'd like to add to it is that temperature is another crucial factor. Low-end machines have very fluctuating

There's a very good sibling answer. Something that I'd like to add to it is that temperature is another crucial factor. Low-end machines have very fluctuating temperatures. Therefore, when one buys a machine in this range, they have to perform tricks, or accept inconsistency. With my machine for example, I have to run two empty cups before reaching the acceptable temperature, for _every espresso_ (as it drops quickly); I'm fine with it. Machines like the Gaggia Classic require the so-called "surfing", which I've never tried. I suspect that Nespressos have a very small group, which makes temperature more predictable and quick, for the intended use, which I guess is less frequent shots. This is speculation on my part. Again, one can be perfectly happy with low-end machinery. There's nothing wrong; just let's be clear that consistency is not what you get with it.