ZEC’s $19.0 billion today is just nominal market cap; there’s no need for that much capital to flow in to maintain the market cap. Many “air coins” whose market caps have already gone to zero once had market caps higher than ZEC.

ZEC’s real market cap is actually $0, but $100 million worth of mining rigs inventory value is a real, tangible cost. Compared to 0, $100 million is almost infinitely large.

Once this round of mining-rig distribution ends, and with no sign of news about the next generation for a long time, the Ponzi scheme will basically be on the verge of collapsing. The logic—this applies to PoW as well—except for BTC: $ZEC