were too mean to by food and beer on a train--
------- (various US meanings of mean) but almost never in the sense of frugal--

No, not frugal, but as b-y rightly says - miserly.
If I had meant "frugal" I would probably have used, "careful," "shrewd" or the good old Scots phrase, "canny."
In the UK, we use all of the other meanings of "mean" as well, though.

*a statement i recently read-- proving Twain's axiom-- "There are 3 kinds of lies-- lies, damn lies and statistics."
Surely this famous remark is attributed to Benjamin Disraeli, English Prime Minister at end of C19, not the celebrated Mr Clements?