The cost of a TradeRoute in a SubRegion seems higher than the original cost.
Eisenhelm-Easthaven: 2.8->6.3
Fairfield-Easthaven: 5.5->12.6
Fairfield->Eisenhelm: 2.8->8.8
...
I examined the Eisenhelm->Easthaven route, and it became longer because of greater zig-zag on a finer Voronoi mesh. It might be possible to fix this by smoothing (skipping intermediate Voronoi mesh points) but that might lose track of altitude gains and water crossings. I'm not happy about this, but it might not be a "bug".
The cost of a TradeRoute in a SubRegion seems higher than the original cost.
Eisenhelm-Easthaven: 2.8->6.3
Fairfield-Easthaven: 5.5->12.6
Fairfield->Eisenhelm: 2.8->8.8
...
I examined the Eisenhelm->Easthaven route, and it became longer because of greater zig-zag on a finer Voronoi mesh. It might be possible to fix this by smoothing (skipping intermediate Voronoi mesh points) but that might lose track of altitude gains and water crossings. I'm not happy about this, but it might not be a "bug".