Quite funny, most of the rich people I've come across in life wouldn't give the impression they had money from looking at them, tight as you know what, hence how they made their money.
Quite intrigued to see the painting now though, where's the so called gallery and what does the painting look like?
You could go back in and take a digital photo of it and when challenged say 'your happy to speak to me now then?' to which you can add 'i'm just taking a snap and to frame it as that costs nothing, as do manners, good day!'