http://lm.i2p/nojs/knowledge/dynamic-block-size?dismissNotice=true
For example, if the miner would lose 0.5 XMR by raising the block size, and the sum of the paid transaction fees would be 0.4 XMR, then there would be a net loss of 0.1 XMR if they were to raise the size, so they wouldn’t do it. Conversely, if the total transaction fees added up to 0.7 XMR, then there would be a net gain of 0.2 XMR, even though they lose the 0.5 XMR from the block reward penalty, so the miner will increase the size.