It will then be possible to move up to a much higher level, where the annual cost would be around 2k$/year. But, for now, there is no such need, since the current server is capable of supporting about 6~7 years of images, if the pace is maintained.
I used to think that the costs are much higher than that, I imagined a number between 7k$/year to 12k$/year, but with these costs, it does not seem that it is difficult.
Are you the only one who controls the backend, or are there other developers, and are you open to adding some other members of the forum with you? In the end, if site turns into a profitable project, continuity will be certain.