Is Elasticsearch on WordPress really free?

Elasticsearch seems like a great feature but I am struggling to understand its requirements and getting it to work. It seems that the core indexing is free with Cloudways. However what else do I need?

I am aware of the WPSOLR plugin but its price is beyond my client’s budget on this occasion.

I am aware of the ElasticPress plugin which is free but I haven’t been able to get this to work. Do you also need to have a paid account with them?