We must demand that the RNG of Battle Bay be more transparent.

Unfortunately in that case you will never get a peace of mind then. If a statement from us is not enough I don't think anything will. Even if the game would be totally open source you'd still have no guarantees that our servers were actually running with that exact same code.

You don't. The same offer is never given per-player at difference prices. Different players do get different offers however in an effort to make them as relevant as possible. For example, evolution offer from T1 to T2 is cheaper than from T3 to T4 cause the content of the offers is different.

The purpose of these offers were to provide all-included package to evolve your item. Taking away cells and gold would defeat that purpose. T5 evolution takes 40 epic power cells and this is not something you just "easily grind". It takes 40 premium chests to gain them which means 16000 pearls, or 14 weeks worth of premium boxes from calendar and quests.

Locking the thread as the original question about BB manipulating loot odds has been answered and any further discussion would probably just end up being fruitless ranting or arguing.

To summarize: The odds for all items within a rarity are always equal, and they are the same for every player.