At code base SVN 9633, there seems to be a typo in the building cost XML file for Weather Vanes (unlocked by Weather Lore at technology grid x=30 y=19). In the BuildingInfos XML, the "iCost" for Weather Vanes (spelled "WEATHER_VEINS" in the XML) is 2405, while other buildings unlocked at the same technology x-grid offset have iCost=270 (the same as the planned value for x-grid=39 in Thunderbird's master sheet in the "Building Re-Costing Project" forum) ".
Externally, the Technology Advisor screen in my game shows settings-adjusted values of 4028 hammers for Weather Vanes versus 452 hammers for other buildings in same technology column.