Tornupto.2304:

Some Masteries seem to be listed with the wrong experience cost.
I found at least two where the listet cost didn’t match the ingame value.
“Thermal Propulsion” and “Koda’s Flame” both cost 508,000 ingame but are listet with 1,016,000 and 1,524,000.

corresponding page:
https://api.guildwars2.com/v2/masteries/13

Lawton Campbell.8517:

Will look into it; in the meanwhile here’s a tracking issue.