Less than 10K total since implementation... My druid mog head/shoulder/weapon and my shaman mog shoulder and weapons only..
Too much to count.
I prefer to grind my own transmog sets... There's a unhealthy comfort that only a gambling addict can know, from running the the same classic dungeon over and over again, knowing that the next mob could drop the piece of your set...
I bought a battered hilt back in Wrath (few thousand, I don't remember) but other than that, almost all of my mogs are S3 sets and T2 recolors. I spent a few hundred on a white leather set for my panda monk. . .not exactly slimming but I haven't seen anything I've liked for the class.
Less than a thousand gold. I kept all my cool-looking gear ever since I started playing the game, and whatever I don't have I go out and farm.
I haven't used transmog at all this expansion apart from a weapon transmog to get rid of gun sounds. During Cata I had two transmog sets that I farmed myself. That would put my total transmog cost in the few hundred gold range, pretty much just what it costs at the vendor. I liked the look of the sets I used, but I couldn't be bothered to transmog every upgrade I received.
I have hundreds of low level greens and blues sitting in the bank somewhere for the odd chance I'll use transmog again.
I spent very little on transmog. Most of my gear comes from farming anyway.
I used like 200 gold to buy mats for a few pieces from tailoring. The only actual item I got was a pair of epic low level leather gloves.
I will put this another way:
$10 + A multitude of $15
$10 for one of the shop headgear; Multiple $15 for the many months of subscriptions I otherwise wouldn't be paying without transmog feature.
Not so much in-game gold cus I don't have much to begin with >.>
Spent rougly 200k plus countless hours.
The most expensive bulk being buying CMGold for transmog but also I did other whacky shenanigans such as craft the expensive Polearm of Cataclysm just for Transmog, then craft the other one to get the saame Polearm in a slightly different color for ~~13k.
Buying expensive Items is actualyl what helps me stop spending: Before I would mindlessly chase from one transmog to the next, be it expensive BoE Weapon/Set or from old Raids/Dungeons, having spend thousands jsut for the transmogrifiy NPC alone.
But once I found some really expensive Set and Weapon and the mindset was "it is so valuable, you get this one but not anything else after this. You will be finished and not spend a dime" and that is exactly what happened. So I may have spent 200k but will not spend anything again, will remain strong [except on other Chars]
I think I've spent a few hundred gold to buy materials for vanilla recipes.
I imagine it's roughly around 30k with transmog swaps, void storage costs, tips for making stuff, and things I've got off the auction house. Maybe more. I kinda wish they'd tell you. They do keep track of the amount you've spent on hair cuts, so I imagine it's possible that it could actually exist somewhere on the servers.
70 gold maybe
Just don't see the point
I bought the Priest Tier 3 set off the BMAH, which roughly cost me around 80K. My other two toons are wearing Tier pieces that drop in low level raids, so they basically cost me nothing.
Blade of Wizardry
Torch of Austen
Those 2 items are all that I've paid for, for transmog. About 5k (the Torch was a few hundred I believe) total.
Less than 2000g, most pieces I get for mog are farmed. Some pieces, like some greens are stupid expensive on the AH.