[2019] Losing money ( game credits, silver money)

As others have already mentioned, service costs for ships increase as you go higher up in tiers. Furthermore, you need to do more at higher tiers for it to matter, for example, doing 50k DMG at T5 is considerably better than doing 50K at T10.

To help with credit expenditure at higher tiers, ensure you have economic flags and camos mounted as this will help. Ultimately however, playing better will improve your net credits at high tiers.

In regards to Mushashi and Alaska, both of these ships are premiums which as standard have a higher level of credit earning, you can see this in the ships modules tab under ship peculiarities:

Fem,