“Poor” is relative.
“Poor” in the context of a first world country means a lack of freedom, not being able to do the things you want in life because of money.
Most poor people in the developed world are truly limited by their poverty, they’re unable to travel, unable to afford healthy food, unable to do what they want with their time because they must trade the balance of their time for the money they need for survival.
In that perspective, no, there’s no such thing as a poor scientist, unless you count grad students and lab techs; even a postdoc earns 40-50k in the US which is a lower middle class lifestyle. There is a huge difference between making 45k and making 25-32k in terms of the freedom to live your life without constantly being concerned with money. On top of that a scientist is hopefully interested in her work and willingly chooses to study the field instead of being forced to by necessity, and likely could switch to a higher paying job in industry with the same education and qualifications which is not an option for a poor person.
But, to whom are you comparing yourself?
If you’re comparing scientists to equally intelligent and hardworking classmates who go into business or engineering, yes, scientists get paid a whole lot less. Almost any career scientist is choosing to earn a lot less money than they could, to be able to do science.
In that sense, are scientists “poor”? Sure, but so is everyone else who isn’t rich when comparing themselves to rich people! It’s a nonsense comparison. And from a philosophical perspective you can argue a businessman who gave up his passion for money is much more “poor” than a scientist who earns a living following her passion every day.
There’s also the global perspective where being “poor” means you are literally unable to afford shelter, sufficient food, life needs, and an education for your children. And by that definition, no scientist is poor. Although grad students still are.
