It's a linear extrapolation that doesn't take into account the not completely unreasonable chance that commercially viable banana varieties could go [functionally] extinct or that climate change will make it dramatically more expensive to grow them in sufficient quantities such that the price can stay on trend.
Ah yes, the Gros Michel banana. It's the banana my parents grew up with, but is now virtually extinct. Weird story. Even weirder that it could happen again.
