Please reduce the Blue essence price of upgrading a mastery level to 6 or 7 to something actually attainable. Currently, you have to grind multiple levels to get enough blue essence for one mastery level unless you get really lucky and get that specific champion shard for it. Then you have to choose between buying new champions and upgrading your mastery level.
In my opinion, Mastery levels shouldn't be tied to the currency and an RNG system in the first place. Before the BE revamp, it was still fine since BE wasn't tied to IP and the costs were attainable. Now it's just a frustrating hassle.