Hi Angrytoilet.
Please be aware that the monthly subscription billing is for CCU (ConCurrent Users), which are much lower than the DAU (Daily Active Users), let alone the MAU (Monthly Active Users).
From our experience for the average app on Photon Cloud 100,000 MAU translate into 5,000 DAU and 250 CCU. If you had 100,000 CCU (which would put your game into the same league as World of Tanks, League of Legends and World of Warcraft), that would mean tens of millions of downloads/sells of your game.
Here is some more background info about the pricing:
http://blog.photonengine.com/2016/06/photon-pricing-explained/
As you can see, we are far from expensive.
Best news for your usecase last:
We offer a redistributable license for Photon Servers, which allows you to ship Photon Server instances to your endusers. The license allows your game to let your users host up to 100 concurrent server instances with up to 50 users each, which means up to 5,000 CCU, completely free of charge. If you want more than that, please contact us for a price quote.