Your screenshots answer your own question. The tx to mint 1 uncommon goods cost 57 sats, and the price shown in the chart is 60 sats, so he is paying less for the mint than he can sell it for. It looks like there is also an inscription in that tx, so he is probably also minting a brc20 token in the same tx.

In short he is paying real money because it generates him more real money than it costs him.

The price of uncommon goods drops because the network fee rate drops. It has become cheaper over time to mint the rune, increasing supply, dropping price.