I must be missing a key factor in my Cookie math? I'm more of a cookie eater than a cookie thinker.
You are missing nothing from the math, it is absolutely correct. You can get three bakeries (thus full bonus from them) ONLY when you pay diamonds. It is that simple. This event is complete diamond trap. It actually consists of 3 diamond traps:
1) The reindeer sleight (or moose or whatever they are) - 3000 diamonds for mostly useless junk
2) The calendar - it is mathematically impossible to get 32 keys for free. No buts, not maybes, impossible, period. So that's 500 dia per missing key (well, if you really need 200 FPs, which most players will receive at least once per week from Himeji. And the extra upgrade for whole calendar - dunno, might be cheaper to buy the stars. Depends on how many keys will be missing)
3) To have full bonus from bakery you need three of them, again, by the same math, you will get about one and half on average, (PERHAPS you might get two if you are extremely lucky with the matches) for free. In no circumstances will you ever get three for free. It just can't happen, the math is very simple:
40 rush tasks for 10 stars = 400
30 daily tasks for 20 stars = 600
30 daily logins for 10 stars = 300
reward after 38 tasks = 170
total 1470 stars = 147 presents = 147 matches... Each match lights up 1-3 candles, so lets average on 2 = 294 houses lit = 14 times the city. That is 7 upgrades since upgrade is every second prize.
For 3 maxed out bakeries you'll need 15 upgrades, 3 are from the quest line, so 12 need to be obtained from the lit up cities. Not happening.
And yes, you will have A FEW MORE stars in total = from incidents and likely you'll win some in the presents. Still, you will never have enough more of them to change the outcome.
And that didn't count the lvl 1 bakeries which you need to obtain two more somehow - they will be in the lit up city, but I'm not sure whether they'll be between upgrades or instead of the upgrade (didn't get that far myself yet)
So yes, to "win" this event and to obtain full bonus from the main event buildings will cost A LOT OF DIAMONDS.
Unless they change the star reward for the tasks to like 20 for rush and 30 for daily or something like that... Very unlikely, but they did surprised us in the past by making some positive changes. It does not happen too often, but it does happen from time to time. This IS beta after all.
Conclusion - very, very disappointing but not at all surprising. Have fun...