Labor, obviously. That's where all the money in a business goes: paying pesky human employees.

If your employees can suddenly magically do more work with the same pay, that's free money (for you). You can pay fewer employees, or pay them less by threatening to replace them with the magic robot.

The magical thinking version of this is that your productivity gains magically translate into more customers and more sales for the same input cost and labor. The free money is really free because you're a magical special snowflake company and every consumer will want your brand of magic machine outputs and not the other guy's. Where does all this money come from? Do those extra customers even exist? Who cares!

Hypothetical:

Pepsi starts using AI in some magical way that allows them to increase their margins. This allows them to reduce prices while increasing profits. Price-sensitive customers switch from Coca Cola products to Pepsi products. Coca Cola loses some market share, reducing economies of scale, and reducing margins, thus reducing profits. As the cycle repeats, Pepsi moves to dominate the market, and Coca Cola is slowly squeezed down.