Getting a coffee espresso maker for less than a $100 is both a yes and no answer. If you are talking about espresso machines out there that makes this Italian coffee, then yes, it is possible.
But, if you are looking for an espresso maker that makes what coffee drinkers come to know as coffee espresso, then a machine would at least set you back by $500.
This is because in order to get a good espresso, there is a certain extraction formula that need to be apply on the coffee beans. And it needs to have a pressure of no less than 12 bars.
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For espresso machines that are less than $100, being all steam driven machines, they cannot achieve this level of pressure, so the espresso that they extracted would not be able to meet the standard of a real espresso.
So, what is a real espresso? Some call this an experience, but by sight, it must be topped by a slightly golden color crema to be consider a good espresso.
By the way, if you asking for what makes a good espresso, then you are probably just starting to make a brew yourself at home, if that is the case, my personal take is start with a steam driven machine to assess if you like brewing coffee at home.
Out of all the steam driven machines, the one that would make a decent coffee espresso and allows you to have a feel of what espresso making is like would be the Delonghi EC 5.
Retailing for less than $40, this espresso machine is in fact cheaper than some programmable coffee maker. So, this is a perfect machine for beginner or folks that are switching from drip filter coffee maker.