It always puzzles me why people save so much cash. If level 24 is released then perhaps a building will be $150-$180k based on trends. Yes the post office was $207 and if another building is offered like that then you may need $300k max at update. Until you complete quests you can't progress to next level and you'll save money in the meantime.
Also remember the Halloween updates were not with cash but treats you had to earn. If the same thing is done for Christmas then why need the cash.
I have about $125k and saving and think I should be Ok with next update as earn about $80k a day.
Rather buy land and play the game of remodeling my town.
I may have to eat my words but seriously folks no glory really in reaching $1 million cash