The data is pulled directly from AWS docs, the same JSON endpoint their pricing page pulls it from, so the data is always up to date. On-demand pricing comes straight from the feed; the "reserved 1yr convertible (no-upfront)" column is estimated from the on-demand price using a per-family discount, since AWS does not expose a compact reserved-pricing feed.
The reason I built this is because my favorite "goto" tool - https://ec2instances.info/ - has been acquired, lacks updates, has some unfixed bugs and misses some pricing. So I put together this little app to pull the data from AWS docs directly and display it in a sortable table.