How do I budget for server space when making a social media app? (Xpost with r/startups)

I'm looking to make a social media app where users can post pictures to a feed as well as their own profile and I'd like to host those images on our servers. I'm trying to figure out what beta tests and scaling is going to look like in terms of budgeting for costs.

I understand limiting photo size like facebook's max of 30mb per photo and estimating how many photos a user might have up but what I'm unsure of is the costs for each time someone looks at the images.

My limited understanding is that each time some views an image, a bandwidth cost occurs increasing the overall costs.

Can anyone give me an example scenario of how this would all break down for a generic social media app in terms of costs?

I can provide more details as needed but anything you can theorize without them will be appreciated since I will be busy a lot of today but still checking back. Thanks!