I like the idea a lot! But I do see where there should possible be some changes with the medals percentage you get compared to how much you pay.
Since Rubies are hard to get, instead of Rubyx10 it should possibly be Rubyx5. That's only my opinion though. either way, this is a pretty solid idea. Hopefully you can get a staffs perspective on this, maybe there will be something like this in the future.
Let's just hope for the best. :)