Wealthy friends, you’re quick to take offene.
It’s not good manners, but it saves expense.

[Irasci tantum felices nostis amici.
Non belle facitis, sed iuvat hoc: facite.]

Martial (AD c.39-c.103) Spanish Roman poet, satirist, epigrammatist [Marcus Valerius Martialis]

Epigrams [Epigrammata], Book 3, epigram 37 (3.37) (AD 87-88) [tr. McLean (2014)]
    (Source)

The commentary by various authors indicates this is about wealthy patrons pretending to offense or other anger at their poorer clientele as an excuse for not being free with gifts. Closely parallel to 12.13.

(Source (Latin)). Alternate translations:

Rich friends 'gainst poor to anger still are prone:
It is not well, but profitably done.
[tr. May (1629); also as Hay (1755)]

My rich friends, you know nothing save how to put yourselves into a passion. It is not a nice thing for you to do, but it suits your purpose. Do it.
[tr. Bohn's Classical (1859)]

To be angry is all you know, you rich friends.
You do not act prettily, but it pays to do this.
[tr. Ker (1919)]

Rich friends, 'tis your fashion to get in a passion
With humble dependents, or feign it.
Though not very nice, 'tis a saving device,
Economy bids you retain it.
[tr. Pott & Wright (1921), "A Mean Trick"]

You well-off people are well versed only
in cursing out your inferiors:
Un For Giving bitching is quite enriching.
[tr. Bovie (1970)]

You weIl-off friends only know how to take umbrage. It's not a pretty way to behave, but it suits your book.
[tr. Shackleton Bailey (1993)]

Not easy, having money, blood so blue,
Lotta gifts expected for all your crew.
Kinda tacky to get angry and just tell 'em all go screw.
But the rich gotta do
What the rich gotta do.
[tr. Ericsson (1995)]

The rich feign wrath – a profitable plan;
’Tis cheaper far to hate than help a man.
[tr. Pott]

How explain why the conspicuously rich
are so easy to offend? Ask their accountant.
He probably won’t tell you but he’ll know.
[tr. Halsey]