- the per-install fee doesn't kick in until you've passed BOTH the annual game revenue and install thresholds (i.e. >$200k annual revenue on the game and >200k lifetime unique downloads)
- the fee isn't monthly, it's per unique download (poor wording in Unity's chart)
- you only pay the fee on the number of downloads over the threshold
This new pricing will actually decrease the price of using Unity for many developers. Before, if your company's total annual revenue was >$100k, you had to buy a paid Unity license no matter what. Now those company's can use Unity totally free until their game reaches $200k annual revenue and 200k lifetime downloads.
This licensing scheme is actually very similar to licensing the AVC/H.264 video codec from Via LA (for example, if you want to ship a build of Chromium with MP4 enabled). In their case, licensees self report the number of units they've distributed per year and pay a small fee on the number of units over 100k. If you ship under 100k units, there is no fee.