I did not mean to listen: but when someone talks loudly across cubicles...

.. well when someone talks loudly across cubicles, you can't help but overhear.
.
And when someone starts with "I am not being cheap, but..." - well then you know they are being cheap.
.
"..but, why is this flight so expensive? Because it is direct Newark to Toronto?  Can you make the meetings if you fly through DC?  Or Chicago, that would be best."