The main cost of search is developing incredibly sophisticated ML algorithms for parsing search queries, for ranking results, and parsing web pages to provide factual results (like Google's snippets and knowledge base items).
And this is orders of magnitude more expensive than it was two decades ago. Because you've got to compete with Google which has a 20-year head start in throwing the best engineers in the world at these problems.
Nobody's going to use a search engine that isn't at least 90% as good as Google in these things. See: Bing.
