Hey JackG79,
Service cost and the ammunition resupply seem normal. Now where you spent a lot of credits that you chose to is the "consumables auto-resupply". Doing rough math you used premium consumables on all 3 options available to you so automatically you have to cover that many credits.
Questions:
What camouflage were you running? Did it have any %credit earn on it?
Were you running the Zulu signal flag or any of the economic flags?
As you get into the higher tiers the costs become more and you have to do more to make a profit. You can offset this by running certain signal flags and camouflages. The key is you have to increase the amount you contribute to start earning more credits at higher tiers.
If you don't mind can you send a screenshot of your "credits received" section?