If you're really looking to save money, don't touch AWS.
Source: I run the frontend for an interactive "one-page-app" site about 3x larger on a $30 VPS with room to spare.
The backend is:
- $10 VPS with OVH + $10 VPS as a fallback with another provider for my DB. - $5 VPS with OVH to host my central debian package repository.
- About $500 worth of dedicated servers for serving hundreds of TB of files a month (usually below one petabyte though). This is not really relevant to this discussion, because OPs application doesn't have a file serving aspect to it. His application is basically just my frontend and a DB.
- Small files and thumbnails go through cloudflare for another $20 / month. But the main site and most files don't use cloudflare (they'd kick me out if I passed that kind of traffic through them). They serve about 30TB-70TB of traffic a month on my account.