Hold onto the packet for as long as you can vs hand it off to your peer as quickly as possible.
Most networks do "hot", Google does "cold" since their network is almost always better than that of the peer.
For example, a cold potato network may have a link from Dallas to Chicago to New York, while a hot potato network could have a direct link from Dallas to New York.
Cogent uses cold potato and is frequently worse than other transit providers.
(Also, they offer the option to use hot potato and pay them less: https://cloud.google.com/network-tiers/docs/overview )
I'm a Google network SRE, but perhaps I'll get new business cards saying "cold potato engineer".
But their hot potato still costs $65+ per TB at medium volumes and $45+ per TB at high volumes. That is still extremely high compared to normal peering costs.