Cities: Skylines - Financial Districts Review (Carthalo)
This DLC is a bit similar to Green Cities in my opinion, you buy it because you know exactly what you want. It includes a new Financial Office Specialization(they actually upgrade/get taller with levels instead of changing the asset entirely), Banks which are basically just Post Offices from Industries DLC which reduce commercial crime rates (Skyscraper Bank is one of the nicest looking assets in vanilla to me), and of course- the Stock Exchange.
Investments aren't that big of a game changer considering by the time you start investing much you will already be in a comfortable position economically and really is just there to add spice in the mid-late game. I will add that if you have Plazas & Promenades where it feels as every inch of a pedestrian zone costs $1,000,000 it could be more worth it.
Very optional DLC that you get when you know you want... well Financial District(s)/Offices and Buildings. However if it's truly worth $8 is for you to decide, that's the thing of these types of DLCs. If you want my opinion, it is.... ish. Getting on sale is always recommended.
Some criticisms I have is how goofy the Stock Exchange looks when you upgrade it, I absolutely love the first 2 levels of the building. Banks are sort of useless besides being a nice to have and looking nice, as we never really had crime problems in the past. The Financial Offices are nice... when they are level 1 or 3, but to me their level 2s look pretty bland.
Also, you just can't deny a chirper with a monacle.
EDIT: I have just been reminded this DLC also includes five new maps, and they are by far the best non-Content Creator maps in the vanilla game. I especially adore Narrow Passage and Windblown Coast, certainly my new favorite maps in the game, even over the Content Creator maps. Honorable mention to Wyvern Pass, very unique map.