A scientific theory
Isn’t just a hunch or a guess,
It’s more like a question,
That’s been put through a lot of tests
And when a theory emerges
Consistent with the facts,
The proof is with science
The truth is with science.
Science is real (4x)
-They Might Be Giants “Science is Real”
From my experience that depends heavily on the textbook’s content. You can go quite a few editions down in the humanities without any change.
Most first year books can use last year’s edition or even the year before, not for a class of course, but for your own use. Classical mechanics hasn’t changed much since Newton.
Now when you start getting into the “Oxford/MIT/Harvard/Fancy U/ handbook handbook range I’ve seen higher than $150, being used only drove the price up.