ἡ πενία μετρουμένη τῷ τῆς φύσεως τέλει μέγας ἐστὶ πλοῦτος· πλοῦτος δὲ μὴ ὁριζόμενος μεγάλη ἐστὶ πενία.
Poverty is great wealth if measured by the goals of nature, and wealth is abject poverty if not limited by the goals of nature. (Saint-Andre)
This saying (U477) is also attested in Seneca's Letters (4:10):
10. But I must end my letter. Let me share with you the saying which pleased me to-day. It, too, is culled from another man's Garden: "Poverty brought into conformity with the law of nature, is great wealth."' (magnae divitiae sunt lege naturae composita paupertas') Do you know what limits that law of nature ordains for us? Merely to avert hunger, thirst, and cold. In order to banish hunger and thirst, it is not necessary for you to pay court at the doors of the purse-proud, or to submit to the stern frown, or to the kindness that humiliates; nor is it necessary for you to scour the seas, or go campaigning; nature's needs are easily provided and ready to hand.
Bailey also cites Lucretius 5.1117-1119, as echoing this saying:
Yet were man to steer
His life by sounder reasoning, he'd own
Abounding riches, if with mind content
He lived by thrift; for never, as I guess,
Is there a lack of little in the world.
quod siquis vera vitam ratione gubernet,
divitiae grandes homini sunt vivere parce
aequo animo; neque enim est umquam penuria parvi.
parce < parcus
If I remember correctly, Epicurus was not a fan of the Cynics who lived by begging in the streets. So, I don't think πενία should be interpreted as abject poverty or living on the edge of starvation and similar scenarios. Parcus has a connotation of frugality and thriftiness. I can see Epicurus hammering that home, that we don't need great wealth to find pleasure, to be happy. That is a common thread. Πενία and πλούτος are also opposites or antonyms, so that also plays into Epicurus's wordplay that he likes.