I did an analysis of the cost of gold in all the ways you can get it. I broke this down into how much premium time would cost you, with all the ways you can buy it. Wargaming has added so many options and I think it's in a deliberate attempt to confuse the consumer. I'll try to keep this simple.
Gold is available in various packages with the less gold you buy, the more it costs you. All figures are in Canadian Dollars.
Premium time is sold in-game for gold, and in the shop for real cash (pay pal, credit card, etc). There are various costs then for differing amounts of premium time. This will also vary depending on how you pay for it. There are five costs shown in the rows which correspond to the five costs of gold shown above.
The best deal is the cash purchase from the premium shop for 1-year which works out to $8.99 per month. If you buy the biggest gold package, then the 1-year deal in-game you will pay $9.06 per month. The most you will pay is 14.18 dollars by using gold in-game after buying the smallest gold package.
So, what about that 11-11-11 "special"?
11 garage slots at full price are 300 gold each. Premium consumables at full price are 50 gold. 11 days of premium at the BEST cost per day possible is $0.30 (using the 1-year premium cash purchase as discussed above). The total cost will of course depend on how you buy your gold but the absolute best you can do is .0045 dollars per gold. That makes the "special" cost $20.62 if bought for gold in-game. The premium store cost of the 'special' is $26.17 which means they are charging you an extra $5.55 because they think you are stupid. Never mind the fact that garage slots and consumables are frequently on sale, or that you can buy premium consumables for in-game silver. Even if, like me, you can't afford $113.26 gold at one time, it still doesn't add up to a deal unless you are buying the $7.88 gold package for all your gold purchases.
I've posted on this before and they keep doing it. I have no faith that they will ever stop because they are not called on it very often, and it's pretty much 'buyer beware' for online purchases isn't it? Please use the charts above to more easily figure out what things are actually costing so you can get the best deal possible. They are hoping you don't.