The economy has been like this for Tier9-10 ships/tanks in all of WG's games since forever
Highly doubt it will change now, you need Tier8 premium ships/tanks to even out the score or the loss you make on playing tier9/10 ships/tanks , thats just how it is and how its been for a very long time.
No matter what anyone else says, i should know i've been playing WoWS since its alpha and closed beta and i've played WoT for 4-5 years as well , just rarely ever bother to write anything on the forums, i read and lurk, just felt like something needed to be set straight.