I would think the site owner’s cost of being indexed is the same for every search engine that indexes the site.
The benefit varies with the quality of the search engines, and that will vary between search engines, but it does get larger the more a search engine is used, so a cost/benefits analysis may show Google and a few other large ones are the only ones worth supporting.
The benefit varies with the quality of the search engines, and that will vary between search engines, but it does get larger the more a search engine is used, so a cost/benefits analysis may show Google and a few other large ones are the only ones worth supporting.