Every now and then, to test combat, the devs announce combat events at a specific station (used to be skeleton station, is now arena station).
Recently they added respawn terminals to it for better fps battles (don't have to respawn at a station 10 mins flight away now).
The economy terminals are simply so that players can buy weapons and ammo at the station, rather than being limited to only what they brought with them.
And as Meetbolio said, the arena station is outside the safezone so combat is enabled. There are no arenas within the safezones.