Traffic from the network you are currently connected to is much, much cheaper for the ISP.
That's not always true. Eyeball networks are often spectrum-constrained and congested on the last mile. When a DOCSIS network becomes congested, the most common relief is a node-split, and those are very expensive.
That's not always true. Eyeball networks are often spectrum-constrained and congested on the last mile. When a DOCSIS network becomes congested, the most common relief is a node-split, and those are very expensive.