bad money drives out good

Meanings

1. Debased coinage (with low levels of precious metals) replaces purer coinage (with higher levels of precious metals).
2. People hoard good currency and other assets and attempt to pass inferior currency and assets to others in exchange.
3. Overvalued mediocre talent replaces undervalued real talent.

Etymology

Traditional sentiment, both in literal and metaphorical sense, dating to ancient works such as Aristophanes' The Frogs, and appearing in various forms in various Islamic and European medieval texts.