The discounts can be very overpowered and with the governers being slowed in hyperspace it even further incentivizes just putting them on a single planet with a corporation and only using that planet. Also if you stack several discounts you can get prices down to downright broken levels.
I think there should be a cap of 33% discount on any given planet.

Also the corporations should give a 20% discount rather than 30%. Right now if you have a planet with a corporation that is decently versatile it's stupid to use anything else.