C. F. Keil and Franz Delitzsch on Proverbs 19:10

Pro 19:10 10 Luxury becometh not a fool;      How much less a servant to rule over princes.

Thus also with לא נאוה (3 p. Pil. non decet, cf. the adj. Pro 26:1) Pro 17:7 begins. אף כּי rises here, as at Pro 19:7, a minori ad majus: how much more is it unbecoming = how much less is it seemly. The contrast in the last case is, however, more rugged, and the expression harsher. “A fool cannot bear luxury: he becomes by it yet more foolish; one who was previously a humble slave, but who has attained by good fortune a place of prominence and power, from being something good, becomes at once something bad: an insolent sceleratus” (Fl.). Agur, xxx. 22f., describes such a homo novus as an unbearable calamity; and the author of the Book of Ecclesiastes, written in the time of the Persian domination, speaks, Ecc 10:7, of such. The lxx translates, καὶ ἐὰν οἰκέτης ἄρξηται μεθ ̓ ὕβρεως δυναστεύειν, rendering the phrase כּשׂרים by μεθ ̓ ὕβρεως, but all other translators had בּשׂרים before them.