With Postgres, you can do almost everything, also a full-text search, but you still have Elasticsearch, Mejlisearch, etc when you need performance and advanced features. The multitool approach is suboptimal in most cases.
That said, it's up to the individual company to decide if the added cost is worth it. Just because the cost exists doesn't mean it isn't worth it.
If your guy couldn't get a single open source software straight, you had the wrong guy :(
I can only see managed service useful when I had 100X traffic and when strong SLA is required.