I've thought about this many times. I'd love a statement from Blizz for the exact amount. I have no idea how much I've spent though.
WoW SEx3
TBC SE
TBC CE
WotLK CE
Cata CE
MoP CE
SC2 CE
An almost consistent monthly sub since 2005.
Numerous name changes.
Numerous cosmetic changes.
Numerous faction changes.
Numerous race changes.
Numerous realm changes.
Everything in the pet store.
A couple of TCG loot cards.
A couple of Blizzcon streams.
Account verify thing.
Plus all the comic book hardbacks and several of the DC Unlimited figures.
I plan on purchasing the D3 CE's, HotS CE and two Blizzcon murloc pets and a rooster mount. That's at least another 1,300 there already.
Then add it all up and convert it to NZD. I think I might throw up now.
The good thing is I'm running out of WoW related things to buy.