Free software is not a free CRM
Open-source CRM offers a genuinely different commercial model: the licence can cost nothing and the deployment is yours to run. The mistake is comparing a licence of nothing against a subscription and concluding the first is cheaper. A running system needs a server, a database, backups, monitoring, bandwidth, security patches, version upgrades and someone competent to own all of it.
Price the humans, not just the software
Most of the self-hosted total is labour, and labour does not scale down with the size of your sales team. A ten-person business needs the same patch cadence as a hundred person business. That is why self-hosting usually makes sense where an infrastructure team already exists, and rarely makes sense as a saving on its own.