Both Loki and VictoriaLogs are open source and free to use. But they have non-zero costs for the hardware they use and non-zero maintenance and operational costs.
VictoriaLogs is much easier to configure and run properly than Grafana Loki. VictoriaLogs runs smoothly with default configuration. It consists of a single small executable, which stores the ingested logs to the local filesystem. It doesn't break during upgrades because of good backwards compatibility.
Loki, on the other side, requires non-trivial configuration and tuning to run properly. This configuration breaks frequently during upgrades. Loki consists of many microservices, which aren't easy to configure and orchestrate. It stores data to S3 (or any other S3-compatible object storage). This brings an additional dependency, which isn't needed in most practical setups.
While S3 storage is usually cheaper than block storage, the price difference isn't so big (2x) when using HDD-based block storage (VictoriaLogs is optimized for HDD). Also, IO operations at S3 usually requires additional costs, which are frequently overlooked when comparing S3 costs to block storage costs.
Also, VictoriaLogs runs typical queries over logs at much faster speed than Grafana Loki. This is clearly shown in the linked article.
See also https://docs.victoriametrics.com/victorialogs/faq/#what-is-t...