If what you need is storage space for art/content that you can link your patreons for download ( I assume this is what you're talking about ) consider switching to google drive!
I know some people are picky when it comes to cloud storage ( like dropbox, onedrive, ect. ) but literally google drive is the cheapest options I've seen that I'm able to back up + share my commissions/art
to customers that I know of. You can pay 20$ a year for 100GB of storage which I think is plenty for storing crap like that, but they also sell sizes up to 20TB ( but who even needs that much LOL )

Hello, I just went to the dropboxpage and the highest amount you can pay is just 15 € a month, so maybe you got a yearly price?

Because they say that is an option too, that you either pay monthly or yearly.

I'm currently using https://www.primeleap.net/ . I believe they're opening up free applications for clubs soon if you're not interested in the watermarking aspect. It connects with Patreon's API, although your users will have to create a new account on PrimeLeap as well. They've been making some nice improvements lately, along with having a gallery and image viewer. I'm really liking it for showing off comic works.

https://www.primeleap.net/#!new-club

Better link if you're interested. xD
Hosting is free if you don't want watermarking.