Is switching over to Amazon S3 for Drupal 7 image hosting worth it?

So I just have a quick question with regards to using amazon s3.

I have a small Drupal 7 site hosted on a VPS with not too much storage space. I put together the site for members of my School's Photographic Arts Committee to upload photos of School events and projects.

The full-quality photos are stored in a private folder on the server, and the images displayed on the site are watermarked 2048px width ones stored publicly.

I'm worried that I'm going to blow my storage space very fast, and I fear that I'm going to blow my not-really-exsistant budget on using amazon s3 with the module in Drupal.

So, I would like to know if it is a worthy investment using amazon s3, I'll be willing to spend +/- $5 dollars on it.

My monthly usage will include 3gigs worth of uploads and probably 20 gigs max downloads. Obviously slowly increasing.

Also, a bit confused about storage billing, do I have to pay for say my 50gigs worth storage from uploads from previous months, or just the 3 gigs of storage I used this month

PS: I live in South Africa and will probably use the Ireland S3 servers as they have the best latency.

Any feedback much appreciated!

Thanks.