What really blew my mind was that picking 50 for the original block subsidy causes the subsidy amount to correspond to the proportion of bitcoins created in that epoch and also to the proportion of bitcoins left to be created:

First epoch: 50 BTC -> 50% created in epoch, 50% left after Second epoch: 25 BTC -> 25% created in epoch, 25% left after Third epoch: 12.5 BTC -> 12.5% created in epoch, 12.5% left after Current epoch: 6.25 BTC -> 6.25% created in epoch, 6.25% left after Next epoch: ...