$15 for 10,000 Skin Stones is "sometimes" a good deal.
The First Look:
The math behind these $14.99 bundles seems relatively straightforward at first glance, especially when you compare them to the more common skin purchasing option, and that's buying skins directly with money.
You can buy most skins for $14.99.
The cost to buy a skin with skin stones is 5000 Skin Stones, and you get the bonus 3500 Skin Stones on top of the skin itself... that's a total of 8500 Skin Stones for $14.99!
The $14.99 Bundle for 10,000 Skin Stones is a better deal, RIGHT?!?
Yes, but also No.
The Math:
We know from THIS VIDEO (linked below) that 3500 Skin Stones = about 5000 Emeralds.
If you divide 3500/500 you get this: 1 Skin Stone = 0.7 Emeralds.
At VIP15 (this is important later) $1 = 1276 Emeralds
So if we take those baseline values and plug in our variables ($15 USD, 10k Skin Stones)
The bundle is $15, so 15x1276 = 19,140 Emeralds
19140 x 0.7 = 13,398 Skin Stones
13,398 Skin Stones is more than 10,000 Skin Stones
But What if I Don't Have VIP 15?
If you DO NOT have VIP15 (and most people won't) then your value of Emeralds per $1 is going to be less than 1276. I haven't done the math specifically on each VIP rank, but at lower ranks the $15 for 10,000 Skin Stones IS a better straight value than spending $15 on Emeralds
So if I'm less than VIP15 I should Buy the Cyber Monday Skin Stone Bundle?
NO!!
Even at lower VIP ranks, it is still INFINITELY more efficient to buy emeralds and spend them on Outland Chests (if you want skin stones) DURING A SPECIAL EVENT!
While it may be slightly more or less efficient to buy this bundle as compared to dumping emeralds into Outland Chests, spending emeralds during events will reward you with considerably more resources! Not only will you get the Skin Stones either way, but you'll also get $15 worth of Emeralds spent towards an event rewarding you resources you'll also need elsewhere; chaos particles, or titan artifacts, or even more skin stones in the case of the Guardians of Outland event!