Picked by use case, not by marketing budget.
SEMrush is a full marketing platform — SEO audits are one slice. If you only want the audit slice automated, you'll spend $139+/month on features you won't touch. Here are alternatives by what you actually need.
If you spend most of your SEMrush time on site audits and you'd rather get JSON your code can act on, SEO Score API is the cheapest, fastest path. If you rely on SEMrush for backlinks, keyword research, or rank tracking, no API-first tool will fully replace it. For a direct feature-by-feature breakdown, see SEO Score API vs SEMrush.
Run an audit before you commit to anything.