other arguments aside .. Athena costs $5 per 1TB scanned and also supports predicates pushdown to S3 Select. I wouldn't call this expensive, at least in comparison to self hosted Presto.
When your monthly Athena bill crosses whatever it would cost to have 5 or 10 EC2 machines it'll be cheaper to use Trino. At my previous workplace we moved from ~$40,000/month to ~$18,000/month by replacing Athena.
Athena is a very good tool to start with - unless you have super large scale you'll probably not outgrow it. But when you do there's Trino.
I do contribute to Trino - although I was merely a user when that cost reduction happened.
And that's all with the benefit of hindsight - it's hard to know a priori how much cheaper your own deployment will be compared to a managed service or how long it will take to implement. Of course, anecdotes like yours help with that, so thanks for sharing your experience!