Well, not that creative... I would call it more realistic. (Err, do you even have a bookkeeper? if you do, he will know what I am talking about and he can advice you more in this ^.^)
Warmane (and I suppose molten aswell) always said a realm should hold itself cost-wise. With this way of allocation you could get a clearer view on costs and income.
Costs:
Lordaeron is having alot of development costs, however those costs are NOT only for the Lordaeron realm. The development costs should be equally allocated among Lordaeron, Ragnaros and Deathwing.
Why? Because the development does not benefit Lordaeron more than Deathwing or Ragnaros. It only benefits Lordaeron earlier.
With development costs spread out, the costs for Lordaeron will decrease, and costs for ragnaros/deathwing increase.
~side note: I assumed that development is the biggest expense here. GM's, server hosting, and any other costs that have their costs allocated by time or sticked to a realm (looking at you, hosting) obviously can not be spread like that.
In addition to this, you could change the way income is registered. (Hehe, this is the part I always felt as terribly wrong with people donating for other realms they play on less).
Income:
The income from donations could be allocated differently aswell, for example you could use /played time as income dividing key. So if a player has characters on realm X and Y and Z, and he donates for an item on X, that does not necessarily mean that this player donated for realm X only.
If this player spends 90% of his time on Y, 5% on Z and 5% on X, you could allocate the costs just like this. It is "easy" (well ofcourse it is not, but in the long term hell yeah it is) to do this way. Something with armory and played time and counting all characters on 1 account etc. will do.
I hope I gave you some worthy ideas to consider.
TL;DR: if you are interested in bookkeeping, just read it or else skip this thread.